Added dependency for Unipath
Read default configuration from config.ini instead of trying to hardcode them within code
Added MagicConfig mixin that automagically resolves and expands MAGIC_VARIABLE in package classes
Allow config file override hardcoded MAGIC_VARIABLE
Added support for ConfigParser expansion in hardcoded MAGIC_VARIABLE
Interpolate MAGIC_VARIABLE only when name contains "path"

This prevents other variables such as URL getting clobbered as a result
Removed debug prints
Refactored MAGIC_VARIABLE resolver into separate method allowing the function to work independent of whether the variable is declared
Fixed MAGIC_VARIABLE interpolating fails when referenced magic variable is None
Migrate base package class to use the new MagicConfig

From this commit onwards, expect LOTS of things to break.
Migrate Metamod package to use MagicConfig
Refactored BasePackage to use Unipath instead of os.path
Migrated SteamCMD package to MagicConfig and merged redundant modules
Fixed package installation failing even when it is already installed
Temporary hack to let us test stuff until we have a proper package manager
Merge branch 'feature/config' into develop