Design Change: setup branches to build wxWidgets 3.1, 3.2, and 3.3.

The 3_1_5 branch should be renamed to 3_1 and updated so that it builds in a build31 directory. The 3_1_7 branch should be deleted. The 3_2_0 branch should be deleted. The 3_2_2_1 branch should be renamed to 3_2 and updated to the 3.2.4 release, and built into a build32 directory. The main branch is currently building into a build directory, but that should be changed to build into a build33 directory. That way, there's no confusion about which directory contains the desired wxWidgets version.

[Randalphwa]

The other option would be to put the three copies of the wxWidgets code directly into the wxUiTesting project. Initial overhead would be about 150 megabytes. That might seem like a lot, but not compared to the wxWidgets repository itself which weighs in at a whopping 8 gigabytes.