Add support to enable only Debug or Release

[GoogleCodeExporter]

By default Make-it-So will generate targets for both Debug and Release 
configurations. That means both of them are compiled when launching a build and 
results in a huge waste of time when building large projects.

The aim would be to add an option to the config file when you only want one 
target (Debug/Release) to be generated.

Original issue reported on code.google.com by florian.sainjeon on 28 Nov 2013 at 10:59