Make Configurable.config read-only
Separate mpl functions in Config to ConfiguredMPL
Fix indent
Fix long line in boundary_labels.py
Document ConfiguredMPL
Move .lines to ConfiguredMPL
Document ConfiguredMPL.lines
Add Configurable.ax
Rename: Configurable.mpl -> .cax
Rename ConfiguredMPL -> ConfiguredAxes
Merge branch 'refactor-config'

- Separate mpl functions in Config to ConfiguredMPL
- Interface change: .config.ax -> .ax
Fix Configurable.ax docstring
Add AndRegion/OrRegion
Add And/Or to create regions
Use numpy.ma.mask_or instead of add_mask util function
Add test_explicit_regions
Fix ExplicitXRegion._y_funcs
Simplify examples/explicit_regions.py

Thanks to the previous commit.
Rename OrRegion to SameDirOrRegion; Use AndRegion by default
Fix test failure