fixed bug #2399
Fix typo in con-student that broke problem load.

Fix up some indenting.
Merge branch 'master' into jingxian2
Merge branch 'master' into jingxian2
added check expression for empty string
Bug fix to re-enable the equation box in the node editor of affected nodes when a node is deleted.
Merge branch 'master' of https://github.com/bvds/LaitsV3
The file dojo-install-version should *not* be in git.
Use "git commit -a" or "git add" to avoid this kind of
error.  Don't use "git commit ." and the like.
Merge branch 'master' into haoxuan2
Rename Undo button to "Clear" in algebraic editor
Merge branch 'master' into jingxian2
Code review for renaming Undo button.
Bug Fix 2381
Simplify code for typechecker.  Moved dom.byId() into
checkInitialValue.
Bug Fix 2381
Code review for inputting units bug.
Added a comment with explanation.
Adding message from PM to fix bug number 2396.
fixed sticky button issue
fixed check equation box with unknown variable in student mode issue
Merge branch 'bvds'