Add allowance of duplicate offers.

[PirateSoftware]

Right now a town cannot get two of the same categories under offers.
Please give us a config option to allow this if we would like to.

Currently it just skips duplicates in TownResourceDiscoveryController.java

//Skip category if we have already discovered something in it
for(String material: alreadyDiscoveredMaterials) {
if(category.getMaterialsInCategory().contains(material))
continue CATEGORY_LOOP;

This makes it impossible to give different amounts of the same material.
I'd like to make Low/Medium/High size deposits but this skips based on the Material type.