Use QRect::united instead of unite

The unite() method has been deprecated in favor of united(). In Qt 4,
united() just calls unite(); in Qt 5, it is completely removed.
Add OpenFileGDB read-only driver option to OGR directory drivers (available in gdal-1.11.0)

- Works fine, though sometimes is assigned '-' for a CRS when CRS is unknown (unrelated to driver?)
Merge pull request #1334 from simonsonc/qrect-united

Use QRect::united instead of unite
[Plugin Manager] support multiline breaks in the about tag
[Plugin Manager] Fix voting stars
layer selection identify: show feature count and add an option to get features
of all selected layers.
remove old declaration
Merge branch 'master' into qt5