refactor(block_list): remove uneeded rootscope
refactor(block_list): remove factory function
refactor(block): remove uneeded Injector
refactor(block): remove uneeded exceptionHandler
refactor(block): remove unneeded BlockFactory
refactor(block): remove unused group from BlockType
refactor(block): remove unneeded map of BlockTypes from transclusion.
refactor(block): remove BlockTypeFactory
refactor(block): merge block_type.dart + block_list.dart into block.dart
refactor(block): rename BlockType to BlockFactory
refactor(block): Rename BlockList -> BlockHole; Create BoundBlockFactory
refactor(selector): DirectiveRef now references Directive directly
fix(priority): removed directive priority

Closes #52

Directive priority is now implied by implied by
type of Directive and position in HTML.