Allow mounting from fstab with user option

[n-st]

It would be useful to be able to add a studip-fuse mount to /etc/fstab and mount it on demand (through the noauto and user mount options):

studip-fuse#doe123    /home/johndoe/StudIP.fuse    fuse    noauto,user,ro,allow-other,uid=1000,gid=1000,pwfile=/home/johndoe/.config/studip-fuse/.studip-pw

Problem: Unfortunately, this is impossible at the moment: the user option "implies the options noexec, nosuid, and nodev" (see man 8 mount), which causes studip-fuse to abort:

studip-fuse: error: unrecognized arguments: --noexec

Solution: Since studip-fuse doesn't produce virtual files with executable, suid, or device attributes anyway, both the positive (--exec) and negative (--noexec) can be simply ignored without causing any problems.

[N-Coder]

Fixed by #9