Multi-root support

[xisui-MSFT]

The major UI differences comparing to the original version of CMake Tools are:

1. Status bar (blue bar on the bottom of the screen) should show the “active folder”, and all status after are corresponding to the current active folder. By default, active folder changes based on the file being viewed/edited in vscode. This behavior can be changed by user/workspace setting “Auto select active folder” to false. If so, clicking on the “active folder” on status bar will show a menu for picking the desired active folder. This change does not affect single root case.
2. A lot of commands with “all”/”for all projects”, such as “configure all”, “build all” and “debug all”.
3. For project outline view, top level buttons are changed to “-all” version of the commands.

[terrelln]

Just wanted to drop in and say that I'm really looking forwards to this feature!

[Zingam]

I get an exception with the attached sample project configured as is, which maybe related to this PR.
CMakeMultiProject.zip

[bobbrow]

@Zingam it looks like your sourceDirectory setting is incorrectly configured. You're pointing to a file instead of a directory.

    "cmake.sourceDirectory": "${workspaceFolder}/CMakeProject01/CMakeLists.txt"

I think the extension could be more tolerant of this case. Can you open a bug to address it?

[bobbrow]

For those following, we just posted a pre-release of multi-root support here: https://github.com/microsoft/vscode-cmake-tools/releases/tag/1.3.0-beta

We would appreciate it if you would install it and provide feedback.

Thank you!