Merge branch 'master' into hotfix/update_add_func
Update axis, grid, tools and legends to use the new add* functions.
Used the new add_glyph method.
Deleted unused import.
Update mpl support to use new add* low level API.
Merge branch 'master' into hotfix/update_add_func
Merge pull request #1090 from ContinuumIO/hotfix/update_add_func

Update mpl support and charts to use the new add_* low level functions.