Spilloff container bug fixed

Previously the spilloff containers properties were not completely reset
when the "Refill" button was pressed.
Remove block from Volume Viewer

Now when an object is removed from the volume viewer it is checked
whether this is a valid removal (e.g., that we haven't created two
distinct objects).
No init on press step

When pressing on this step on the navigation panel the init function is
not run, which was previously redrawing stuff.
postpilot
post pilot bug fix

In the previous commit, with a bunch of changes, steps after the first
were not loading.
Library objects down

When placed in library objects go to the bottom of a cell.
Builder clean up (shift)

From last commit cleaned up saving function to remove unnecessary code
that shifts object in volume viewer.
Library background color

Now library has a visual location for each model.
scale

New scale model will be used to show digital mass.
Author view

Now can write prompt in rich text editor.
beaker overflow

If water goes above top of beaker makes a puddle. Water level cannot
exceed top of beaker.
Ray cast beaker

Now addition of objects to the beaker is done with ray casting of a
single fixture below the level of water until rest.
display ordering of objects placed in beaker

now keeps track of how many objects are in beaker, places objects in
world accordingly
in process of building models for sink or float

While developing a set of working exercises made some changes to events.
Also: A sub-array of premade objects now allows randomization.
A premade object can be given a field is_mystery.  Which hides it from
inspection.
Made some changes to prevent our automated tests from failing.
Merge branch 'master' of https://github.com/WISE-Community/WISE-VLE
Merge pull request #234 from jonvitale/master

Improved Box2dModel
increased default per-request limit of epigame step
increased default per-request limit of SurgeNode step
Updated NetLogo 5 jar to v5.0.3 (should fix NL problems with Java 7 on OSX)