At initialization, it creates an empty source file and copies the CMAKE files needed for VALA

Now the CUSTOM command supports both files and folders
Now always adds the GLib namespace.

Now only adds CUSTOM_VAPIS_LIST when there are a custom VAPI list
Fixed the removing of CUSTOM_VAPIS
Now forbides to set files in the main directory (all files/folders must be inside a folder in the main directory). This is a must to avoid failures.

Updated to version 0.20
Updated documentation