Added JS load() search path extensibility:

Configurable via ctrl/sbbs.ini file JavaScriptLoadPath key value
(comma-separate listed of search directories), default value is "load".
This list is exposed in the JS object model via the js.load_path_list array
(may be modified by scripts).
For JSexec, the default load path list may be over-ridden with the '-i' option.
For relative load paths (e.g. not beginning with '/' or '\'), the path is
assumed to be a sub-directory of the (configurable) mods or exec directories
and is searched accordingly.
So, by default, load("somefile.js") will search in this order:
mods/load/somefile.js
exec/load/somefile.js
mods/somefile.js
exec/somefile.js