Use the XWiki sheets system instead of the include macro

Example: when you create a flag, the content of the entry is

{{include reference="ForumCode.FlagSheet" /}}

instead of using a ClassSheetBinding.

Same in the FlagClass, the code is:

{{include reference="XWiki.ClassSheet" /}}

instead of using a DocumentSheetBinding.

This is not the recommended practice as it can lead to some issue (see XAFORUM-192).

So the idea is to replace everywhere the include macro is wrongly used by the sheet system (not only the Flag).

Are concerned:

• FlagClass
• FlagTemplate
• ForumGithubDescriptor
• MostActiveTopicsPanel