Request for review: Grepview plugin rewrite

[George Syron]

  I have finished the major rewrite of the grepview plugin. Short list 
of changes:
- no external tools needed anymore
- full PCRE support
- pseudo-treeview in the outputview
Known bugs:
- showProgress and showMessage from IStatus do not seem to work, but I 
cannot track down where the error is
- finding the files still blocks the UI; could be solved by writing a 
hybrid algorithm of iteration and recursion, but that would decrease 
code maintainability and readability

Things that could still be improved:
- custom templates, so that users can add their own templates
- multiline matching is currently not supported
- perhaps add also "Replace in Files"

Thanks for comments,
-- Syron