Re-enable ability to change sorting in search result lists - alternative approach

Currently, it's not possible to change sorting in search results from the default "search relevance".

When searching for a file users sometimes have problems with locating it in long lists of search results, and have no way of improving this situation manually.

To fix that, re-enable sorting in search result lists via the view menu options in case of grid view, and clicking on columns in case of the list view.

This merge request is an alternative approach to !577 (closed) and does the following:

• adds "Relevance" column in the list view that shows only in search, just like the "Trashed On" is available only in trash
• adds "search relevance" to sorting option in the view menu in grid view that shows only in search, just like the "last trashed" is available only in trash
• re-enables ability to change sorting options in search by showing the sorting options in view menu for both list and grid views

Screenshots:

Fixes: #374 (closed)