[Monocle] Refactored TextSearchHandler parts to RequestSearch().
[Monocle] Const-correctness.
[Monocle] Use non-static data member initializers.
[Monocle] Emit TextSearchHandler::gotSearchResults() for #1694.
[Monocle] SearchTabWidget stubs for #1694.
[Monocle] Separate code to {Clear,Build}Highlights().
[Monocle] Non-const TextSearchHandlerResults members.
[Monocle] TextSearchHandler::SetPreparedResults() for #1694.
[Monocle] Store all required data in SearchTabWidget tree.

For #1694.
[Monocle] Handle items activation in SearchTabWidget for #1694.