TC: Add open-close block helpers

[tolu]

Added helper methods for TeamCity blocks

Usage

Target "MyTarget" (fun _ ->
  sendOpenBlock "MyTarget"
  // target code here
  sendCloseBlock "MyTarget"
)

This nifty little thing gets you from this:

to this (targets in an expandable tree view):

Futures
As a next step it would be awesome to use this feature by default in the target output (when running in TeamCity) instead of going the long way round and polluting every target with sendOpenBlock / sendCloseBlock.

[forki]

thx

[dahlbyk]

Would it make sense to model this as IDisposable?

Target "MyTarget" (fun _ ->
  use sendBlock "MyTarget"
  // target code here
)

[forki]

I think you should not use this in user code. It should be used in target and task helpers.