Change default shortcut for the predefined URL template

[neocotic]

The Ctrl+Alt+U seems to no longer be picked up by Chrome (on Windows at least, and for me) and, although this can be changed, I want to change this default shortcut to avoid this problem for normal users.

Suggested shortcut: Ctrl+Alt+T

This will be less important once #201 is implemented but is probably still useful for normal users.

Important

During the update process ensure that the shortcut is only changed if the URL template currently has the default shortcut (i.e. U) and no other template uses the new shortcut (i.e. T).

[neocotic]

Perhaps not Ctrl+Alt+T as this opens the Terminal on some systems.