Uncomment first derivative optimization (#3356)

This was commented due to a now fixed libmes/fparser bug
git Deprecate 'read_legacy in SolutionUserObject
(closes #3355)
Merge pull request #3484 from dschwen/chparsed_3356

Uncomment first derivative optimization
Merge commit '3ab8e5020e1594029ace62e701c957ea3bd553cd'
Merge pull request #3482 from aeslaughter/xda-3355

Deprecate 'read_legacy' in SolutionUserObject
Merge commit 'cdb7d9bf6061d160e849c294325ec8054e441e58'