QPID-5260: Significant tidy up of cmake build
* Move to cmake 2.6 as minimum required version
  (2.4 is extremely long in the tooth now)
* Add control over building individual language bindings
* Make settings you don't usually want to change advanced
  so they are hidden by default
* Changed to a uniform naming scheme for options:
  ** Options controlling what to build are all BUILD_
  ** Options controlling features of he build are ENABLE_
  ** Options controlling internal aspects of the qpid runtime are QPID_
* Respect the BUILD_TESTING option so that we won't build the
  tests unless it is set (it is by default)
* If we don't find the boost_unit_test_framework then don't fail,
  just don't build the unit tests (this is motivated by one of the
  Apache Jenkins ubuntu builders which has this set up)
* Tidied up some of the detection of external dependencies to make it
  more idiomatic cmake (but there is more to do here)
QPID-5261: Install DLLs and import Libs to more usual places for a windows SDK
QPID-5262: Install debug versions of MS runtime DLLs
QPID-5263: Fix boost files on windows.
- As we no longer install any header files with boost dependencies we can stop
  shipping any boost includes files in the windows kit.
- Install correct Boost DLLs.