fix typos
unify method names
gtlua: fix sequence extraction
gtlua: fix gt.translate_dna()
gtlua: add meta node accessors
add dev tool for spec checker
gtlua: add 'genome_node:get_line_number()'
add GtSpecResults
add gt_comment_node_(try_)cast()
add spec results support
add detailed spec check reporting
src_clean
gtlua: add comment node methods
add spec checker output for more node types
cosmetics
add feature_node:appears_as_child_of_type()
gtlua: implement sequence node bindings

Closes #289.
some more improvements to spec checker
cosmetics
change wording of spec checker messages

inspired by http://www.methodsandtools.com/tools/tools.php?rspec