Further cleanup of the pickup code regarding autowielding and autowearing

Essentially cleaned up two things (both of which were an issue before adding hands-free code):
* auto-wearing things picked up from the ground was dependant on whether you were armed or not
* there was a dead branch in pickup code (apparently it was trying to make use of player::is_suitable_weapon(), but the way the pickup function was written, the code was never triggered. Furthermore, the branch used hardcoded values for volume overload, instead of can_pickupVolume, which factors in stuff like mutations etc.

With these changes, dressing up as a shower victim should be finally as convenient as it could be ;-)
Sorry, no experience with bionic weapons here - do we also prevent player from wearing/taking off armor manually (so via inventory or 'w') when wielding a NO_UNWIELD weapon? If not, I don't see a point of preventing this added convenience here.