make workers distribution more intelligent

Let's say priority for Titan is 10 and Deterium is 5. This makes the
manager try to assign twice as much of the avialable workers to titan
than to deuterium (instead of just filling all titan mines first).
Later on, when there are many buildings, this is much more useful.
Revert "make turns in build menu be the minimum needed ones instead of the current ones"

This reverts commit 37ef61048d4ff581d46adbff118a5c754ca29812.

How nice I found a good reason to revert the garbage.
For some reason, this code interfered with the manager's worker
distribution calculation when putting something into the build list.
introduce priotity 0

Disables the corresponding resource for more precise control in the
priority algorithm
It can still get workers later on in case some are left though.
limit priority range to 10
fix a problem if there a no workers to distribute