Example building

[rpavlik]

Fixes up CMake so that:

• consuming apps of the cmake config can actually use the cpp target and have a chance of finding the corresponding deps as well.
• the examples cmakelists.txt file can be used outside of the build tree.
• only examples where the source and all dependencies are present are built. (so undesired examples can be disabled just by deleting their source files)
• a test can be automatically run to verify that the examples continue to build reliably as a separate project.
• examples are included in the installed zip file (getting them into the SDK is another task)

Partially addresses #228 (the SolidColor change is included here) and all but the last commit from #247 is also included.