Extensively rewrite and clean up hammer

 - Support for building AppImages/AppBundles with "release_ember" command
 - Relocate all support scripts to "support" directory
 - Cleanups to enhance ease of understanding and maintainability
 - All build artifacts actually end up in the "work" directory now
 - All existing functionality maintained fairly transparently
 - Move all variables likely to be modifed (e.g. library version numbers)
   to start of hammer.sh script
 - Temporary -DOIS_INCLUDE_DIR hack due to Ogre 1.9.0 not building correctly
Separate sources and build artifacts.

Sources are now put in "source" and build artifacts in "build".
Remove unused Ogre features.
Only checkout if we're not on "dev".