Cleanup obsolete projects, build scripts and files

[BrainCrumbz]

After some chatting and thanks to @amirrajan review, here's a list of obsolete items that should be removed from repository:

• [x] NSpec.GallioAdapter project
  • in dedicated branch
• [x] NSpec.crunchsolution.local.xml files in several projects
  • in #137
• [x] .nuget folder
  • in #137
• [x] VS 2012 solution
  • in #137
• [x] TDNetRunner folder
  • in dedicated branch
• [x] .userprefs
  • in #137
• [x] watcher_dot_nets.rb, dotnet.watchr.rb scripts
  • in dedicated branch
• [x] nspec.watchr script
  • in dedicated branch
• [x] red/green.png files
  • in dedicated branch
• [x] .DotSettings (TBC)
  • in dedicated branch

Further related changes:

• [x] Adapt CONTRIBUTING.md where it mentions dotnet.watchr.rb

This is to ease porting to .NET Core, so ideally should be done before that or at same time.

[BrainCrumbz]

@amirrajan items left to check/edit/delete are solution NSpec.sln.DotSettings file and CONTRIBUTING.md. What to do with those? Tnx

EDIT What about libs\ directory? From a text search it seems that's not referenced anywhere. Nevermind, Rakefile needs that.

[amirrajan]

I'll take a look.

[amirrajan]

I updated CONTRIBUTING.md. I'm fine deleting the .dotsettings file.

[BrainCrumbz]

Great, thanks about update!