Changes to layer property dialog for unique value renderer.

[jpalmer]

This is a follow on from ticket 399. Currently when using the layer property dialog with POSTGIS layers, the user may experience large application hangs when using the unique value renderer methodology (as maybe others). For a user friendly experience the classification field listbox should not be automatically populated in all cases. Instead one of the following would be acceptable:

1) The user is warned that a query is about take place and that it might take some time. 2) Same as above but only if the layer feature count is above some thresh hold value 3) The listbox is not populated at all, and the user has to select the classification field then click a populate button to fill the listbox. 1) and 2) might still apply in this case.

[mhugent]

In svn 0.9, possibility 3) is implemented

[(none)]

Milestone Version 0.9 deleted