Bug in cmake install: not all necessary headers get installed

[louis-langholtz]

Expected/Desired Behavior or Experience:

Using CMake's install capability as follows, installs all necessary files:

cmake --install

Actual Behavior:

Installation doesn't actually install all necessary header files. Specifically, it misses installation of files like the following:

PlayRho/PlayRho.hpp
PlayRho/Common/Acceleration.hpp

The only file from PlayRho/Common that appears installed is the Real.hpp file. All of the others are missing.

Steps to Reproduce the Actual Behavior:

1. Build the project, then run the above mentioned cmake install command.
2. Look inside of the install location for PlayRho include files.
3. Notice that files like enumerated above are missing.