Instance configuration updating when using RevisionUpdateAdapter

[Filipsi]

As of now, RevisionUpdateAdapter provides following functionality:

• Addition, update and removal of mod-loaders
• Addition, update and removal of mods
• Addition and update of mod resources (config files)

Ability to update environment configuration is not implemented. This feature comes in handy on servers for updating motd or player cap.

The RevisionUpdateAdapter should have configuration flag in modpack definition that allows specification of environments where configuration feature is enabled.