Allow development time deobfuscation of mods to an MCP target

This PR adds property `fml.forcedDeobfuscationPrefixes`, which allows users to force classes to be deobfuscated, even when using unobfuscated environment. When using unobfuscated code both raw and srg names are converted to versions used in rest of codebase.

Option can be used to easily test interactions with closed source mods without reobfuscation.