GROOVY-6268: section on keywords and possibility to use keywords as identifiers after dots
GROOVY-6268: shebang line comment
GROOVY-6268: use font-awesome's icons
GROOVY-6268: multiline comment section
GROOVY-6268: correct escaping for the multiline comment delimiter
GROOVY-6268: Maven docs
   * fixed cross reference links
   * added sections on GMaven, GMavenPlus, GMaven2 and Groovy Eclipse
   * fixed leveloffset