Addressed code review comments
Removed attribute code generation pieces
Addressed code review comments
Add TagHelper parse tree visitor.

- The visitor looks for TagBlock's that match registered TagHelpers and rebuilds them into TagHelperBlock's.
- Added the code generator and corresponding chunk for a TagHelperBlock.
- Added syntax tree specific objects & helper methods to create accurate tag helper structures.

#71
Reverted code generation specific pieces.
Addressed code review comments
Rebased and changed visitor name.
Renamed file.
Addressed code review comments.
Addressed code review comments
Reverted code.
Addressed code review comments
Addressed code review comments.