Implemented resizable panels using jquery-ui

All of the resizing happens in layout.js.
Layout.css has also been modified as jquery-ui-resizable needs relative
position to work.
Fixed resizable panels for safari

Safari doesn't support the use of calc() in css.
Use minified jquery and custom jquery-ui
Fix leftpanel height on window resize
Set limits on resizing to ensure no breakage

Addresses problems with resizing things too small/too far.
Fixed issue w/ toolbar overflow in small windows
Reimplemented without using jquery

Based off splitter example linked to in
https://github.com/increpare/PuzzleScript/pull/132#issuecomment-40552219
Improved resizing behaviour on quick drag to max

Also refactored resizing into functions
Reset dragbar locations if < 1/2way on resize
Tweaking maximum drag extents
Set drag extents at LHS border and toolbar bottom
Miscellaneous fixes

* Remove 1px gap
* Remove 30 as a magic number
* Make sure that LHS border and toolbar bottom are the minimums even on
window resize events.
Move dragbars simultaneously with window resize

I wasn't quite able to get proportionate movement to work, but moving
the bars so that space is given to the editor on horizontal resizing and
to the gamecanvas on vertical resizing seems to feel ok.
Tabify spaces to keep consistancy
Use proportionate resizing on "big" resizes

Using proportionate on small resizes is more difficult because the
dragbar locations get snapped to the nearest pixel.
Drag cursor improvements

* Use drag cursors from mouseDown till mouseUp
* dragbars now move to centre on the drag cursor
Tweaking pixels to improve hdragbar response

Re-introduces a subpixel (i.e. stays 1px even when zoomed in) gap, but I
think maybe that can be fixed some other way.
Limit min dimensions to 100px, remove sfx form

Known issues - on window resize to zero, get error - graphics.js:
INVALID_STATE_ERR: DOM Exception 11: An attempt was made to use an
object that is not, or is no longer, usable.

After this, the layout gets clobbered.
Merge branch 'master' of https://github.com/increpare/PuzzleScript into resizable-panels-jquery-ui

Conflicts:
	js/graphics.js