[diagrams] Usability improvements
 * Choose default attribute value for interpolation if none is set
 * Remember last used tab
 * Default for scale dependent visibility matches layer settings
[diagrams] Show message on messagebar instead of messagebox
And some indentation updates
more spelling fixes
catch system signals and stack trace on linux
html identify results: catch loadFinished only once
[sextante] added back script creation tools to toolbox
[sextante] fixed help edition dialog.
[sextante] edited description of OTB orthorectification algorithm
[pyqgis-console] some fix for find text in editor
- changes tabs to north
[pyqgis-console] minor fixes and cleanup
[pyqgis-console] fixes translation strings