UI tweaks

[oBFusCATed]

Please check this https://github.com/obfuscated/codeblocks_sf/commits/ui/tests branch out.

The main changes are:
1. replace boxsizers with std dialog button sizers
2. make all std dialog button sizers to expand
3. replace all calls to wxGetSingleChoiceIndex with a custom function that uses PlaceWindow and allows setting the size of the window
4. some other minor sizing changes

So the main change is related to 1/2. It will result in the ok/cancel/close buttons to be located on the right side of the dialogs in both wxmsw and wxgtk. As far as I can see this is where the buttons are supposed to be. I cannot test on osx, but I suppose they'll be placed where people expect them.

Any objections against pushing these changes in svn?