Parser Progress Check-in

1. Merged Lexical Token definitions back into one
   single definition again for easier escape processing.
   Just remove the backslashes once during the lexing
   stage.

2. Removed unnecessary prototype definitions from
   ASTNode and LexToken; The LexToken's prototype
   definition proved to be of little help.

3. Added a slice wrapper for ParserBase, which is used
   to extract a range of tokens to the InlineParser.
   That way, there's no need for a second lexing pass
   in the paragraph (inline) context.

   All the block parser needs to do, is to determine the
   token boundary of a paragraph, then offload the grammar
   to the inline parser.