minimaps generation

[bloerwald]

• being a blp format is third priority.
• light is second priority
• water is 1.5-ish priority
• wmos are 1.5-ish priority
• m2s should be rendered, but only depending upon filters and size_cat, as blizzard does (take a look at what they do, it is a huge mess)
• priority 1 though is actually saving the right thing, not some utter mess.

For sake of doing world maps or allowing for editing, one may want to export them at higher resolutions as well.