Add support for %-variables in arguments
(like in ContextMenu and ToolBar plugins)
Correct scripts detection:
* check only for *.js and *.vbs
* fix detection of *.JS and other upper case-based variants
See FillScriptList() in AkelFiles\Plugs\Scripts\Source\Scripts.c
Fix description for -script argument
Small optimization: i++ -> ++i
Switch to use AkelPad.GetArgValue()