- Introduce MANUFACTURER setting to set package manufacturer via CMake.
- Introduce COMMUNITY_BUILD setting to be passed on to packaging
  (not used here, but required for our own packages to determine what
   added files should be included in the package).
- Create an RTF version of the COPYING text file and use that as the
  default license (can be overridden by providing a COPYING.rtf file).
- Allow passing extra arguments to candle and light via environment.
  (Need -sval in pushbuild, but want validation elsewhere.)
- Introduce a custom action that stops and uninstalls the service 
  if the user installed one that points into the MySQL directory
  that is being removed.
  (Our own packages historically used the instance configuration wizard
  for this, but it wouldn't be very nice if MSIs created by our users
  couldn't remove it too.)
- Make install location configurable again ("Browse" button in custom
  installation was greyed out before).
- Remove registry keys that use "MySQL AB"; they should only be set in 
  packages provided by us. Users can set their own registry keys if
  they want to.

Note that a read only copy will still exist  in the ProgramFiles directory
(so it can be reused for other instances)

WITH_LIBGCC %define, it isn't subject to shell rules and is
parsed anyway.  Instead create a file with optional files to
include.

setup for now, leave large changes to later.