don't plug the cord for halt

- Do a proper shutdown, or the filesystem cache
  might not have been written to disk.
print a small info message when skipping an already build platform
add some more docs about the boxes
cleanup and fix the extraBins copying

- fix: make one extraBins folder per OS, previously this was
  accumulating extraBins files during consecutive builds

- prepare the extraBins folders for all OSes in one step

- copy the extraBins with all other folder in one scp -r call
set LATEST=v2.065.0-b3 for cleaning

- this prevents dlang.org to fetch all tags
use shallow clones

- saves a lot of time for downloading uneeded history
Merge pull request #59 from MartinNowak/unforcedHalt

don't plug the cord for halt
Merge pull request #60 from MartinNowak/skipInfo

print a small info message when skipping an already build platform
Merge pull request #61 from MartinNowak/boxInfo

add some more docs about the boxes
Merge pull request #63 from MartinNowak/fixExtraBins

cleanup and fix the extraBins copying
Merge pull request #64 from MartinNowak/setLATEST

set LATEST=v2.065.0-b3 for cleaning
Merge pull request #65 from MartinNowak/shallowClones

use shallow clones