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
fixed #133
Improved resizing behaviour on quick drag to max

Also refactored resizing into functions
only regerate text when necessary. should be ok
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.
editor fixes
fixes #135
fixes #136
Drag cursor improvements

* Use drag cursors from mouseDown till mouseUp
* dragbars now move to centre on the drag cursor
left click on level text in console to select all of it
cmd+left click on level text in console to load level