CMake conventions

[biagas]

Describe what needs to be documented.

CMake conventions being adopted through the CMake reorganization effort should be documented. The list below can and should be updated with new ideas as the occur.

• [ ] CMakeList.txt required for all subdirectories, including info on how to handle libraries where source files are in multiple subdirectories.
• [ ] Use of BLT.
• [ ] How to write a Find module for proper import and installation of Third Party libraries.
• [ ] Explanation of visit-defined cmake macros and functions.

Is the documentation missing?

Yes, I looked in the Style Guide. It should be a new section there.