Ability to enable MediaProxy and Invalidation from MediaProxy tab

Closes #141 (closed)

added 3 commits

• 8f8a916f - Dispatch URL Search when removing and purging urls
• a58143e3 - First green test
• 8eef51ad - Add tests for fetching media proxy settings, evicting single and multiple urls

Compare with previous version

mentioned in commit 38936ff4

merged