Added SmartIndent provider (currently disabled).

Disabled because it doesn't play nice with VS converting spaces to tabs.
Need to find out how to register Dart to appear in Language options too.
Project change for earlier file rename.
Tweaked error types so warning don't look so scary.
Added basic IPeekableItemSourceProvider that doesn't work :(
Update analysis package.

Plus references to new files in following changesets.
Initial tooltip implementation.

Maybe buggy; feels a bit hacky to make it Async :-/