nuspec updates

tidy up catch blocks after MvvmCross#580

Missed from last commit for MvvmCross#563

3.1.1-beta5 nuspec changes

remove multiple enumeration of attachments enumerable

3.1.1-beta2 nuget version changes

Do *not* checkin Components

3.0.14 nuspec changes

When child windows with their own binding contexts get detached/reatt…

…ached, let's cache their datacontext for that operation - fixes issue with custom MvxSpinner