[2.2] Add efficient unparking in batched forcing.

This helps each thread reach its full potential, and in particular the
single-threaded workload is markedly improved.
Removed annoying compiler warnings.
Merge pull request #3356 from pontusmelke/remove-compiler-warnings

Removed annoying compiler warnings.
Merge pull request #3343 from martinfurmanski/2.2-efficient-unparking

Add efficient unparking in batched forcing.
New spectrum execution monitor for batch importer

for better overview of relative step processing costs in the stage(s)