Replace "Remove current sequence" with "Remove sequence"

Behavior in the current UGENE version

In the current UGENE version a sequence from a multiple alignment can be deleted as follows:

1. Using the "Edit > Remove current sequence" item in the sequences names list context menu. Note that there is no corresponding item in the main menu.
2. Using a hotkey ("Delete" on Windows, "Fn + Backspace" on Mac OS X).

When several sequences are selected and the actions are used, all sequences are removed in case 2, but only one sequence is removed in case 1.

Required solution

Therefore, the following should be done for consistency and usability:

1. Add item "Remove sequence" to the "Actions->Edit" menu, when multiple alignment is opened. Remove item "Remove current sequence".
2. Both "Remove sequence" actions must do exactly the same as the hotkey action, i.e. if several sequences are selected, they all must be removed.
3. Show a hotkey nearby the menu items. The hotkey must take into account the current operating system.