CSS tweaks, probably only temporary
Added RandoriCssElementDescriptorProvider and configured it in the plugin.xml
fixed extension prefix for css description provider
Removed the RandoriCSSSCompletionContributor and replaced it by the RandoriCssElementDescriptorProvider, which gives a far simpler way of adding our custom completions
Added another check that makes sure the custom CSS completions only happen in a Randori project
Merge pull request #64 from rolandzwaga/develop

New implementation for custom CSS completions