Fix Bug number 2393
bug fix 2398
fixed bug #2399
code review for ritesh changes
Fix typo in con-student that broke problem load.

Fix up some indenting.
Merge branch 'master' into jingxian2
Merge branch 'master' into jingxian2
Clean up of 'sessions.md' file.
added check expression for empty string
Fixing typo in dodos problems.
Merge branch 'ritesh'
fixed check empty expression message
Merge branch 'master' into pradeep
Merge branch 'pradeep'
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