Changes 1.7.3:
* Fix 3581 Ftools: union tool leave holes in output
* Fix 4500 Simplify tool freezes QGIS
* Fix 4466 Fixes for 'v.what.vect' and 'v.generalize' modules in the GRASS
  plugin
* Fix 4552 Patch for v.what.vect
* Fix 4035 Print Composer shape combo box not refecting current shape
* Partial Fix 3097 Add preference to set/override environment variables
* Fix 2749 Move 'Add to Attributes List' button
* Fix 4560 Wrong scale displayed in Map canvas
* Partial Fix 4383 Ftools: Improve how processes are handled
* Fix 3577 Adding a print composer doesn't dirty the document
* Fix 3170 Many GDAL Tools don't work in OS X standalone
* Fix 3723 Transparency settings are not applied from *.qml
* Fix 3576 qml not read automagically for rasters
* Fix 2977 Messy uninstallation of the standalone installer
* Union and Symetrical difference works only on whole layer fixed
* Save some time in node tool for geometry export and avoid detachs
* Initialize default symbol to 0 in rule based renderer
* Make relative paths default
* Fix tab restoration in project properties
* Add helpful info to GdalTools Settings dialog on how to configure GDAL path
* New vector layer dialog - show CRS as authid-description pair instead of
  proj4 string
* Fix crash with relative file paths if projPath is not yet defined
* Add helpful info to GdalTools Settings dialog on how to configure GDAL path
* And a lot of other smaller Bugfixes

(adam)