side value bugfix and few improvements

* Fixed Side value's name in set_side_value statement (was "sideValue",
should be just "value")
* Fixed a typo in the space map form menu: "Make whitespace names" ->
"Mark whitespace names"
* Added help page for the space map hotkeys
* Added option to open help form from the space map
* Warnings about expressions are now underlining whole variable/literal
instead of only first letter