Remove old TODO: removing duplicates from overridable members

This was for an edge case that has not occurred in (manual) testing.
Rename AutoCompleteBufferContext -> BufferContext
Make BufferContext work with any Request derived class

This way the BufferContext class may be used in other contexts than
AutoCompleteRequest
RunOverrideTargetRequest: inherit Request, not AutoCompleteRequest
Make overrided member indent properly
Make sure the overrided member gets formatted properly
Don't create a new ParsedResult - use the existing one
Disallow trying to override in e.g. interfaces or enums
Merge branch 'feature-complete-method-overrides' into develop

Conflicts:
	OmniSharp/OmniSharp.csproj
QuickFix: add new static constructor with DomRegion, IDocument
StringExtensions: add MultipleWhitespaceCharsToSingleSpace()
MultipleWhitespaceCharsToSingleSpace: add example
QuickFix.ForFirstLineInRegion(): Trim() result Text

Helps with readability
QuickFix: add ForNonBodyRegion static constructor
QuickFix: add ForNonBodyRegion overload with no specific BodyRegion
Add features for navigating the AST in the current file
Merge branch 'feature-current-file-members' into develop