STORM-151 : Modify llkdu cmake to point explicitely to static libs, simplify make (in progress, don't pull yet)

Modified llkdu pointer for all platforms, cleaned up unused kdu-binaries references, fixed llkdu cmake to simply point to lib and build

Reintroduce check for LLKDU source after downloading the prebuilt lib, to avoid adding a build dependency on it.

Now building with llkdu can be skipped by specifying INSTALL_PROPRIETARY=OFF when configuring the build.
Reviewed by palmer

dataserver-is-deprecated
for-fucks-sake-whats-with-these-commit-markers