introduce support class level system for stores

[karolherbst]

I think we should categorize stores in some way, so that we can explicitly say how good stores can be supported in theory or in the future.

I was thinking about something like that:

class 1 support level:

• stable and documented API for accessing content, changes will be announced at least one week earlier
• helps gamekeeper by fixing bugs, providing documentation, implementing API
• no external software required

class 2 support level:

• API which changes only when needed (like adding new login methods, introducing new conten feature like DLCs)
• doesn't work against gamekeeper (eg: by making the API unstable)
• external open-source software needed

class 3 support level (aka: we don't what we can, but guarantee nothing):

• unstable API, which can change at any time without reason
• requires external closed-source software

class 4 support level (aka: no support at all)

• does explicitly work against gamekeeper (if it comes to law stuff, we might have to abandon support fully)

[karolherbst]

discussion on IRC