Integrate improved parser (bel_parser) into bel.rb.

[abargnesi]

bel_parser provides full checking of syntax and semantics for BEL expressions and BEL script.

This should be integrated into bel.rb to provide:

• Expression validation
• Autocomplete
• BEL Ruby DSL
• Nanopub translation
• BEL generation
• Expression parser (included with bel_parser)
• BEL Script parser (include with bel_parser)
• Supplant lib/bel/{annotation,namespace}.rb with lib/bel/resource/....
• Remove unused functionality (likely moved to bel_parser).