Fix loading errors in ACR, AR and cFBPConvNet

[cslht]

Fix errors that prevented three models from loading or building their parameters.

• ACR and AR imported ModelParams, which doesn't exist in LIONmodels (the class is LIONModelParameter), so both raised ImportError on import. Also, ACR.__init__ type-hinted ACRParams (undefined) and AR.__init__ used LIONParameter without importing it; both now use LIONModelParameter, matching the base class.
• cFBPConvNet inherited from LIONmodel.LIONmodel (class used as a module) and raised AttributeError at class definition; now inherits from LIONmodel.
• cFBPConvNet.default_parameters() did params = ModelInputType.IMAGE, overwriting the parameter object with an int and raising AttributeError on the next assignment; it should be params.model_input_type = ModelInputType.IMAGE.
• ACR.default_parameters() set params.input_type, an attribute nothing reads, leaving model_input_type as None; now sets params.model_input_type.