rcll-central: prevent instruct goals for RS from being dispatched when there is an active fill goal for the same RS.

[snoato]

Filling an RS changes the wm s.t. the fill counts are updated. An active instruct goal for an RS has a grounded PDDL precondition, which can be invalidated through the updated counts (even when the count is increased) due to modelling constraints. This can lead to the instruct to fail due to timeout and to a potentially gamebreaking unrecoverable state. An easy solution for such situations is to just prevent instruct goals while filling. Better (mid-term) solutions would include updating the domain to handle actual numbers (switch from STRIPS to another PDDL standard) or to use locking predicates. Since this is up for discussion, the easy solution should be implemented for now.

[TarikViehmann]

The immediate issue is fixed through #588, but regardless of that it makes sense to integrate proper number representations.