NF: add deprecated.py module with tests

Add helpers for deprecating modules and classes
RF: move minc module to minc1 name and deprecate

Move minc.py to minc1.py and add deprecation shells for old imports.
NF: First pass at MINC2 loading with tests

Add MINC2 loading - very basic, with no save.
Inherit MINC1 tests
Add example file and check loaded parameters against mincstats
DOC: expand docstring for MINC2
NF: add MINC2 to standard imports

Add Minc2Image to top-level namespace.
TST: add MINC2 to image API tests