[Qgis-developer] Merge of Arun's summer of code work

[Martin Dobias]

Hi all

I am happy to announce that I have just merged Arun's work on
symbology. He has done a great job and after some testing I think the
code is ready for prime time.

What to expect?
- style manager has been greatly improved:
  - grouping of symbols (including child groups of groups)
  - tagging
  - "smart" groups (showing only symbols matching some criteria).
  - search
- symbol selector and properties dialogs have been integrated to just
one dialog, improving the usability a lot
- style database is now stored in a SQLite database rather than an XML
file for better scalability
- style import improvements: load style directly from given URL,
saving imported symbols into a group
- SVG fill: shows directories for easier traversal through the SVG directories
- surely some more goodies I've forgotten to mention!

Please note that with the transition of styles to SQLite database you
will find your style empty - but don't worry! You can import all your
saved symbols and color ramps from ~/.qgis/symbology-ng-style.xml -
from now they will be stored in ~/.qgis/symbology-ng-style.db.

Arun: thanks for your hard work and I hope you will continue to
contribute to QGIS! :-)
Also many thanks to Nathan for co-mentoring and lots of great ideas
for the GUI improvements that landed in the code.

Regards
Martin