Definiton of Actions
--------------------

click:     press one (or multiple) mouse button(s) and
	   release them without moving the mouse

click+mod: hold down a modifier key (Shift or Ctrl) and
	   click.

drag:      press one (or multiple) mouse button(s), move
	   the mouse, and release the button(s)


Table of Actions
----------------

                   | click  | click+mod   | drag
------------------------------------------------------------
left               | select | select add. | rotate
------------------------------------------------------------
middle (in text)   |  toggle text select  | move/resize text
------------------------------------------------------------
middle (elsewhere) | select | select add. | move molecules
------------------------------------------------------------
left+middle        |        |             | zoom
------------------------------------------------------------
right              | popup  |             |
------------------------------------------------------------
