IITC Dialog Overhaul, part 2

Core changes
* window_management.js => panes.js (clarity, distinction from dialogs)
* Make portal preview use dialogs instead of the large preview "window"
* Use `open' callback instead of `create' callback for all dialogs
* Replace collapse/close buttons with themed buttons inspired by the AP Gain plugin
* Dialogs can now gain and lose focus, with changing title bar
* Tweak the Poslinks window to use dialogs
* Add collapseCallback, expandCallback, collapseExpandCallback, focusCallback, and blurCallback
* Fix http <img> in About dialog that caused Chrome to complain

Plugin changes
* guess-player-level 0.4.1: Use dialogs with titles, typo fix
* portal-counts 0.0.8: Use dialogs with titles, typo fix
* portals-list 0.0.12: Don't hijack every single dialog onscreen, add titles, typo fix
* scoreboard 0.1.8: Use dialogs with titles