Parallel target execution / Progress information in console

[tunger]

This implements #162 and #107.

Main changes

• Redirect Logger output to InMemoryLogger instances per thread.
• Adds two build strategies: sequential and parallel
• Adds progress reporters:
  • Progress bar (ShellProgressBar) when running as console (i.e. not on redirected outputs)
  • Log per target: when running parallel on redirected outputs
  • Continuous: write logs as they come (current behavior)
• Adds BuildTimeEstimator to get sense of progress.

Usage

Opt-in to parallel build: Use ExecuteAsync in your NukeBuild class instead of Execute. Furthermore, if you provide the flag --no-parallel, it will always run sequentially.

Logger usage remains the same and is agnostic of threading from the view of the caller.

Open

• Test performance impact of progress bar.
• If there are lots of invoked targets, the progress bar grows from bottom of the terminal upwards, overwriting initial output.
• ParallelExecutionPlanner can very likely be improved.
• Commit 1b74097 is a fix for current problems on develop and can be removed afterwards.

I confirm that the pull-request:

• Follows the contribution guidelines
• Is based on my own work
• Is in compliance with my employer