Update CMakeLists.txt to install only .pretty

[jsreynaud]

Modify installation to install only *.pretty directories.
All other directories (for example CMakeModules) should not be installed.

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[poeschlr]

I assume you tested this?
@tijuca you seem to know something about make files, is this ok?

[jsreynaud]

I had tested it under Linux. Not yet under Windows/Macosx

[tijuca]

This is probably the better and correct approach as this installs only the specific folders. Currently I can't test this but I guess Jean-Samuel has done this. I can test this later once I'm home again.

My bad I haven't seen this issue from Jean-Samuel.

[poeschlr]

Thanks for looking into this.