Skeleton modules in place for loading/saving 'perspectives'

fsl/data/strings.py

fsl/fsleyes/__init__.py

fsl/fsleyes/actions/copyoverlay.py

fsl/fsleyes/actions/loadperspective.py

fsl/fsleyes/actions/openfile.py

fsl/fsleyes/actions/openstandard.py

fsl/fsleyes/actions/saveoverlay.py

fsl/fsleyes/actions/saveperspective.py

fsl/fsleyes/frame.py

fsl/fsleyes/perspectives.py

fsl/fsleyes/platform.py

fsl/fsleyes/views/__init__.py