Allow gmx tune_pme to skip the check for command-line health

Therefore, this patch adds the "-check" command line option, which is
TRUE by default, but can be switched to FALSE in problematic cases.
Documented its main use case in the error message that it would
circumvent.

Also corrected a few typos.

Fixes part of #1609

Change-Id: Id1cadd620438c36c123ff075c9a98ea7d1534d4d