Add option to use a shared directory for dependencies

[makamys]

The problem

Currently, if a mod requests a dependency, it will always be stored inside <instance dir>/mods/falsepattern. This means if the same dependency is requested in multiple instances, a copy of it will be stored in each instance. This can cause a lot of disk space to be wasted if you have many instances. For example, ArchaicFix depends on fastutil, a 22 MB library. I already have 3 copies of it on my computer in falsepattern directories, and I am certain this number will keep growing.

Suggestion

In AssetDirector, I have outlined a standard for specifying the location of a shared data directory for Minecraft instances. One way to solve the problem would be to follow it:

• If the minecraft.sharedDataDir JVM flag is set, <minecraft.sharedDataDir>/mods/falsepattern could be used
• If the MINECRAFT_SHARED_DATA_DIR environmental variable is set, $MINECRAFT_SHARED_DATA_DIR/mods/falsepattern could be used

[FalsePattern]

Added this to the mod, available in 0.9.4+