Use search term as window title in Search window

Use the search term in the Search window's window title, instead of "Text Search".

Currently, it is possible to have multiple Search windows in OmegaT, which is great, but on a taskbar they all have the same title, namely "Text Search". So a user has to cycle through all of them to find the results that he is looking for.

So, use the search term as the window title, so that the user can see directly on the taskbar, when viewing the minimised Search windows, which window is the one he is looking for. -- leuce