Feature Request #152: Change Soldier to Ship in Soldier Screen

This works as follows:

- Right-clicking on one/more soldiers multi-selects the soldier(s), akin to Ctrl+click.
- Shift-right clicking selects a block of soldiers at once, starting from the most-recently selected soldier.
- After the above, left-clicking cycles through the available craft and assigns the soldiers if there's room.  If any of the soldiers are wounded, a warning appears and disallows the selected soldiers from being assigned.
- Crafts with no room or that are out at the moment are not considered for selection.
- If NO soldiers are currently selected via right-click, then left clicking will bring up a soldier's info screen as per normal.

This pull request also includes a change to the TextList class and allows for multi-selection by use of a new boolean flag.  Shift+right click block selection is built in, and right-clicking is akin to ctrl+clicking.

Looking forward to feedback/corrections/bugs/etc.