Allow penalised movement of furniture even if it's too heavy.

Currently I find it strange that a player with below average strength (`str < 8`) is suddenly unable  to move anything at all.

This change will allow the player to try and move the object, but take significantly longer with risk of strain (increased pain).

The chance is dynamic and based on the difference between our strength and the weight of the furniture.

Feedback messages have been inserted to let the player know if the thing is too heavy when they grab it, when they injure themselves, and if it's taking a long time to move.