Reference Bugsnag nuget package.
Remove old Bugsnag code.
Fix code to work with Bugsnag nuget library.
Migrate Tests to nuget Bugsnag library.
Skip linking Bugsnag libraries.
Fix Bugsnag nuget number.
Merge pull request #341 from toggl/roosmaa-bugsnag

Use extracted Bugsnag library.

Extracted the Bugsnag library into a NuGet package and started using it
instead of the one in Phoebe.

Closes #170

Conflicts:
	Tests/Tests.csproj
	Tests/packages.config