Implement Search and Browse Functionalities

[cgiovando]

A placeholder to keep track of ideas for implementing search and browse functions.

• allow seamless overlay of image search results with already opened QGIS layers
• search results should be displayed dynamically in the same window of the search/filter functions
• this portion of the plugin should have similar functionalities that are available in the OAM Browser
  • filter based on metadata
  • sort of results
  • footprints and image overviews

[yojiyojiyoji]

moved to #87