Updated minimum cmake version to 3.1
Added checks in findllvm script to handle old 3.4 LLVM version
Added back include directories needed by old LLVM version in ICG.
* Merging changes from cmake branch to master
* Fixing includes for renamed header files
* still need build rule
* Adding warning for swig code for gcc8+
* Adding CMakeLists.txt for data products
* Cmake merge #901
Making adjustments to get cmake working on the Mac (Mojave)
* Cmake merge #901
Changing string append to list append
