[FEATURE] allows to store SQL queries in the DB manager
Update labeling gui and add expression support as data defined value

- Add QgsDataDefined class
- Add QgsDataDefinedButton class
- Add data defined Python support
- Add standalone SVG selector dialog to QgsSvgSelectorWidget class

- Fix for #4607, show only pertinent fields when setting a data defined value
- Fix for #5048 and #5049, data defined settings are literally used
- Fix for #5726, number formatting does not work for expressions
- Fix for #7755, using bufferSize to enable/disable label buffer is confusing
- Fix for #7779, labels do not register in label collision engine; and for #4719, inactive options in labeling dialog
- Prepare label text's expression upfront when preparing layer; makes rendering much faster
- Change name of 'feature obstacles' to appropriate terminology
Turn off buffer size-trigger fix for <2.0 projects until better solution is implemented
adding new language Bengali on request
[pyqgis-console] uses context menu to handle the command history instead of typing directly the command into the console
- shows history in dialog (much more usable)
Reduce margins in properties dialog
Adding missing test data files
Merge pull request #598 from ccrook/master

Adding missing delimited text data files
Debbuging NoGeometry support in QGIS WFS Server
expression translation fixes
german translation update
enable/disable layer dependant actions:
- select by expression requires active layer
- labeling requires and active vector layer
Update Mac INSTALL notes

- Fix registered copyright symbol in .t2t files
[pyqgis-console] increases height of the row in QListView and QTreeWidget for Windows OS
- small fixes for the run script command
[pyqgis-console] small fixes
update script for translation files
fix #7853
Merge pull request #600 from slarosa/master

Update translation script
yet another german translation update
[Fix #7877] Crash when saving layer style as qml