[Ide] Fix execution target list unexpectedly changing.

HandleConfigurationChanged could added at an unexpected time, resulting
in the target runtime being changed unexpectedly in response to
execution targets changing. This was observed whenever
IPhoneDeviceManager handled a device change.
[Core] Change the default PCL profile to Profile78
Updated reference to md-addins
Updated reference to xwt
Merge pull request #489 from LogosBible/ExecutionTargetReset

[Ide] Fix execution target list unexpectedly changing.
Fixed 'Bug 18061 - Incorrect "delegate subtraction has unpredictable result" warning'
Bump nrefactory.
Merge remote-tracking branch 'origin/master' into fsharp

Conflicts:
	version-checks