use WLIntegerArray for csBuf and csArg in WLTerminalFeeder

* more refactor
reimplement the QuickLook support of downloaded items

* use public QuickLook API only
minor refactor of coding style
update DBPrefsWindowController to the version by kgn
reformat WLTermView.m

* add some comments
* use NSDictionary for attributes cache
replace deprecated API using CoreText