server does not start if data.json is missing defaultPath

[a-b-r-o-w-n]

The app needs to be more resilient against changes to the data.json structure. If there is an existing data.json, the app should migrate it to the newer version without breaking.

Steps to Repro

1. create a data.json with this contents:

{
  "storageConnections": [
    {
      "id": "default",
      "name": "This PC",
      "type": "LocalDisk",
      "path": "<your home path>/Documents/Composer"
    }
  ],
  "recentBotProjects": []
}

(notice no defaultPath)
2. Start the app.

~/src/BotFramework-Composer/Composer (master) $ yarn startall
yarn run v1.13.0
$ concurrently --kill-others-on-fail "npm:runtime" "npm:start"
[start] npmnpm WARN lifecycle The node binary used for scripts is /var/folders/_9/5k2ch04j1fsgwnt81_b175n00000gn/T/yarn--1574270706842-0.43671951124321007/node but npm is using /Users/chriswhitten/.nvm/versions/node/v12.13.1/bin/node itself. Use the `--scripts-prepend-node-path` option to include the path for the node binary npm was executed with.
[start]  WARN lifecycle The node binary used for scripts is /var/folders/_9/5k2ch04j1fsgwnt81_b175n00000gn/T/yarn--1574270706842-0.43671951124321007/node but npm is using /Users/chriswhitten/.nvm/versions/node/v12.13.1/bin/node itself. Use the `--scripts-prepend-node-path` option to include the path for the node binary npm was executed with.
[start]
[start] > @bfc/root@ start /Users/chriswhitten/src/BotFramework-Composer/Composer
[start] > cross-env NODE_ENV=production PORT=3000 yarn start:server
[start]
[runtime]
[runtime] > @bfc/root@ runtime /Users/chriswhitten/src/BotFramework-Composer/Composer
[runtime] > cd ../BotProject/CSharp/ && dotnet build && dotnet run
[runtime]
$ yarn workspace @bfc/server start
$ node build/server.js
[start] internal/validators.js:112
[start]     throw new ERR_INVALID_ARG_TYPE(name, 'string', value);
[start]     ^
[start]
[start] TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined
[start]     at validateString (internal/validators.js:112:11)
[start]     at Object.dirname (path.js:1129:5)
[start]     at PathHandler.dirname (/Users/chriswhitten/src/BotFramework-Composer/Composer/packages/server/build/utility/path.js:27:31)
[start]     at StorageService.createFolderRecurively (/Users/chriswhitten/src/BotFramework-Composer/Composer/packages/server/build/services/storage.js:148:57)
[start]     at /Users/chriswhitten/src/BotFramework-Composer/Composer/packages/server/build/services/storage.js:109:22
[start]     at Array.forEach (<anonymous>)
[start]     at StorageService.ensureDefaultBotFoldersExist (/Users/chriswhitten/src/BotFramework-Composer/Composer/packages/server/build/services/storage.js:108:37)
[start]     at new StorageService (/Users/chriswhitten/src/BotFramework-Composer/Composer/packages/server/build/services/storage.js:153:14)
[start]     at Object.<anonymous> (/Users/chriswhitten/src/BotFramework-Composer/Composer/packages/server/build/services/storage.js:156:17)
[start]     at Module._compile (internal/modules/cjs/loader.js:959:30) {
[start]   code: 'ERR_INVALID_ARG_TYPE'
[start] }
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
error Command failed.
[start] Exit code: 1
[start] Command: /Users/chriswhitten/.nvm/versions/node/v12.13.1/bin/node
[start] Arguments: /usr/local/lib/node_modules/yarn/lib/cli.js start
[start] Directory: /Users/chriswhitten/src/BotFramework-Composer/Composer/packages/server
[start] Output:
[start]
info Visit https://yarnpkg.com/en/docs/cli/workspace for documentation about this command.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
[start] npm ERR! code ELIFECYCLE
[start] npm ERR! errno 1
[start] npm ERR! @bfc/root@ start: `cross-env NODE_ENV=production PORT=3000 yarn start:server`
[start] npm ERR! Exit status 1
[start] npm ERR!
npm ERR! Failed at the @bfc/root@ start script.
[start] npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
[start]
[start] npm ERR! A complete log of this run can be found in:
[start] npm ERR!     /Users/chriswhitten/.npm/_logs/2019-11-20T17_25_09_932Z-debug.log
[start] npm run start exited with code 1
--> Sending SIGTERM to other processes..
[runtime] npm run runtime exited with code SIGTERM
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

[a-b-r-o-w-n]

@liweitian We should also allow this to be configurable (for environments such as test, CI, etc). Please support COMPOSER_BOTS_FOLDER environment variable.