Network optimizations, resourcepack changes, Underground layers, bug fixes

Changes:

• Now map being send to player only if it has been changed (network usage optimization)
• Added non-square markers support

• Added ability to override marker size using markers.sizes config property.
• underground-layers and WorldGuard support (Thanks @meisosi !)
• Added config property allow-config-updates to disable automatic config updates.
• Added configurable delay for cache loading
• Added world validation (remove cached tiles for non-existent worlds. validate-worlds config property)
• Added optional supported_formats for pack.mcmeta for compatibility with another resourcepacks (use-formats config property)
• Fixed bug with missing markers on respawn
• Fixed bug with /mm admin stats access without permission