Updates to validation workflow based on in-person discussion

[spwoodcock]

TODO

Validating individual features:

• Clicking on a building that is already mapped on the management frontend, should give an option to 'Validate Now'. This loads the submission detail page, where the manager can approve or mark as has Issues.

Note we should remove the option of 'rejected' to simplify things - only use has Issues.

Mapping all features in a task:

• Clicking on a task that is mapped, should give the option to 'Validate Features'.
• We open a separate view, where all remaining features to be validated are loaded together.
• We have a 'next' / 'previous' workflow where we can validate each feature on by one.
• Option to mark as completely validated.