solidity scanner takes triple slash doc comments into account

- Conditionally scanning for the documentation comments and gettings their
  contents.

- Adding tests for this functionality of the scanner
fixing typo and alignment
documentation comments are now always skipped but saved as special tokens at the Scanner
styling fixes
extra comments scanning test
cleaning up the external interface of Scanner::next(). No special cases
simplifying scanDocumentationComment()
Merge pull request #524 from LefterisJP/sol_parse_comments

Solidity scanner taking documentation comments into account