Pass src_properties and dest_properties in projection specifiations

[Tobias-Fischer]

This little PR changes the projection specification methods to get src_properties and dest_properties passed, rather than the projection itself for which the parameters are set.

[jlstevens]

Doesn't look like this one can be merged in anymore. Please rebase your fork!

Otherwise you suggested changes make sense but I will note that a few things will no longer be accessible when defining projection parameters:

• The projection type - should be known to the modeler as the parameters being specified will be chosen for a specific projection type. The decorator also makes this obvious...
• The source and dest sheet types. Shouldn't be an issue and could be added (automatically) as a property if really necessary.

As I don't think either of these things are really necessary, your changes do seem like a nice improvement. Hope resolving the merge conflicts won't be too painful...

[Tobias-Fischer]

Done. Regarding your comments: The projection type is definitely be known. I don't think it's necessary to access this. So far, I have not encountered the necessity to be able to access the sheet types. But as you said, should this in future change, it is an easy fix to add that as a property.