Refactored Tooltip code to remove some MonoDevelop UI dependencies

Moved Tooltip code to SymbolHelpers
Refactored to use defined Symbol helper patterns
Merge pull request #745 from 7sharp9/TooltipRefactoring

Refactored Tooltip code to remove some MonoDevelop UI dependencies
Added support for Entities that are delegates

e.g. Action<T>
tips are displayed the same as other functions with the addition of a
line `delegate of`:
type TypeName =
   delegate of
      ’T1 *
      ‘T2
          -> unit
Merge pull request #747 from 7sharp9/AddTypeDelegateTips

Added support for Entities that are delegates
Merge pull request #1 from fsharp/master

Merge changes from master