Metadata improvements

[BryonLewis]

resolves #206
resolves #207

• Regular expression icon added to search fields
• The linking and filtering using regular search expressions is working so the data can be pasted in the system.
• Fixes and Improvements to adding/deleting metadata
• Added option to 'Purge' deleted keys (this will delete the value from all metadata in the system, not just remove it from the filters).
• Processing loading indicators for updating and deletion of tasks because depending on the number of metadata fields it may take a while.

TODO:

• Update client dev and job linking in the interface to link to the / root path instead of /girder. The /girder path is causing issues when jumping back to DIVE.
• Add a refresh button In the Metadata Editor that will reprocess the existing data and recalculate the min/max and any fields that are available.