Implement MaglaDependency functionality

[jacobmartinez3d]

MaglaDependency objects will be associated to various MaglaEntity types and should mirror the look and feel of a basic requirements.txt and be able to retrieve information about the specific modules and packages defined in it's dependency list. For a first implementation it is ok for this feature to only work with packages and modules which are accessible via the local filesystem.

Example use-case for a MaglaDependency record:

There is a shot which requires a newer version of Blender than what is set at the project level. A MaglaDependency record would then be created and associated to the desired shot and would have only 1 dependency defined - the version of Blender desired.

When magla comes accross any entity with an associated MaglaDependency it should attempt to use its definitions over the defaults for whatever operation is being performed.