make install support

[Teklad]

Adds better support for "make install". ResourceManager now does lookups in standard share directories and cmake properly adds the "resources" directory to its install targets.

[joolswills]

Thanks. Short on time but will check / review soon.

[gllmhyt]

Hello, thank you for this patch. But even with this, I'm still getting an error with my build directory used to search resources for fonts apparently:

May 21 10:06:21 lvl0: 	Error - File type unknown!
emulationstation: /home/postblue/Documents/Projets/PKGBUILDs/emulationstation/src/EmulationStation-2.9.1/es-core/src/resources/Font.cpp:21: Font::FontFace::FontFace(ResourceData&&, int): Assertion `!err' failed.
[1]    90162 abort (core dumped)  emulationstation

I'm trying to make a working PKGBUILD here. When built, the packager complains about references to source directory for the files usr/lib/libpugixml.a and usr/bin/emulationstation. Can you please have a look at it?

[gllmhyt]

Follow up: this patch enables easier packaging solutions using make install, creating /usr/share/EmulationStation but I end up with resources in /usr/share/EmulationStation/resources/resources and not /usr/share/EmulationStation/resources.