Fix default cmake build type for windows

Apparently the default build type on windows is "Debug" (at least for
cmake-2.8.11), while the default on linux is the empty string.  Finally
found a sane method for overriding cmake defaults - set them before
project() is called :-D
First attempt at cpack packaging
Much improved windows package

* Install Qt and system libs as required to make a self-contained
  package

* Add license file to give installer somewhere to look
  (annoyingly, you can't turn off the license screen completely
  when using cpack)

* Deduce version number directly using "git describe"

* Install to correct location (avoid x86 directory for 64 bit build)
Fix minor MSVC warnings