Many small fixes to new script commands

Decided to fix other stuff while I'm at it:
* Fixed "set_side_value" and "set_special"
* Added custom menus for set_side_value and set_special
* Fixed limits and editing form for elite ability bits
* Improved "set_ship_text" and "start/end_getting_keypresses_from"
statement texts
* In many cases with these commands added dropdown for names (to select
object name from a list of objects created somewhere in the script)
* Added additional hotkeys to checklist (consoles and ability bits)
forms: tilde for all and numbers for exact items
* Allowed up to 29 skyboxes and manual input of any number