Added opening a new tab on double click on tab background (ref #305).
Rearranged global functions in lua spec for simpler grouping (ref #79).
Removed unused parameters.
Updated default colors to have less contrast (ref #305).
Updated default folding to use lighter colors (ref #305).
Disable function call indicator by default to reduce clutter (ref #305).
Reduced the line number margin width and default font size (ref #305).
Fixed an issue with running processes not terminated when closing IDE.

This was a side-effect of an earlier change that was done to run
end-callbacks before terminating external processes (as those callbacks
may be used, for example, to remove temporary files).

Many of interpreters had logic in those callbacks to reset debugger.pid,
which was useful (at a time) to reset UI after terminatin of a process
(introduced by 4554c67c). However, this logic was unnecesary in
interpreters and interfered with terminating running processes, so this
commit removes it from all the interpreters and does in the IDE itself.
Refactored editor config references.
Added `editor.foldtype` with box, cirle, arrow, and plus types (ref #305).
Increased default font size in the editor (ref #305).
Added explicit conversion to number for numeric settings.
Made fold and marker margins wider (ref #305).
Added `editor.extraascent` option to add line spacing (ref #305).
Improved compatibility with wxwidgets 2.8.
Updated breakpoint/currentline markers for less contrast colors (ref #305).
Added `editor.foldflags`; set default to draw one line when folded (ref #305).
Added wrapped line indicator to line number margin (ref #305).
Added `outputshell.usewrap` to set Output wrapping; on by default (ref #305).
Set def linenumber font size as one smaller than editor font size (ref #305).