fix comments and docstrings misspelled words

Change-Id: I355b6fedf372b1273ceaebe22e8e890aa9c913c9
Closes-bug: #1267103
replace type calls with isinstance

In store/__init__.py, there are two uses of the "type" method to
check type compatibility. It is better to use the "isinstance" method
since it will work for subtypes as well.

Change-Id: I20958aa449822cac2cb03e12557fded3f45a9e05
Closes-Bug: #1267074
Add config option to limit image locations

This patch adds the image_location_quota config option. This allows
a deployer to limit the number of image locations allowed on an image.
The default value is 10. Users will only be able to update an image
if the result of the transaction would be under this limit. This
behavior is intended to be similar to 'quota_metadata_items' in Nova.

We have implemented the same limit for image properties, members and tags,
see:
https://review.openstack.org/#/c/56981/
https://review.openstack.org/#/c/59563/
https://review.openstack.org/#/c/58056/

docImpact
Closes-Bug: #1259031

Change-Id: I0e0033a1d11be267144e8e10b730bb6331263d4c
Merge "replace type calls with isinstance"
Merge "fix comments and docstrings misspelled words"
Merge "Add config option to limit image locations"