Make searching more useful

[tibirna]

Currently, the search function is ensured by the dropdown and textinput dedicated to all searches in the main toolbar. This works well, but it can be modernized.

Proposed workflow:

• user clicks in a column in the rev list view
• column is marked with visible focus
• starting typing something pops a dynamic text input in place of the column head and the content of the rev list is restricted according to whatever the user types
• hitting Enter makes the search definitive (and writes a filter description somewhere visible (with a Clear button to remove it)
• hitting Esc cancels the search and restores the content of the list view
• this will allow adding searches by date (the search widget would be more complex, allowing for start and end date)

Also, the search in the commit content should be made contextual. And search should be added to the modified files list.