Add task to update function configuration and run during deploy

[dmcgillen]

This will update the config for the $LATEST version (not the
latest published version) and then, when the function code is
updated, the next published version (if publish is set) will
get the updated config.

[dmcgillen]

I've added calling this as part of the deploy task. This is how nervous-systems/cljs-lambda do it, which I've used in the past, and found it really helpful as it means you can maintain function config with your project and not have to change stuff in the Lambda console.

[dmcgillen]

Just to mention, there are a few additional boot task options to update-function-configuration that the other tasks don't have, and as I couldn't come up with any sensible one-character names that didn't conflict with those already there, I just left them blank. Hope that's ok!

[lsnape]

Bump. Any chance of merging & releasing this? Thanks!