xF2 Add-on Proxy Link-Forum 2.4.1

• Fix N+1 query behaviour in XF2.1

• Fix that a proxy-forum would not display stats or generate URL's properly

• Add icon
• Prevent mixing protected/public when extending entities

• Confirm compatibility with XF2.1
• Ensure creating link forums without add-on enabled does not error

Rework installer to be more robust.

• Ensure the src/addons/SV/Utils folder is also uploaded! If it exists, just overwrite.

• Remove redundant SQL queries when proxying a forum.

• Tweak execution order of class extensions/template modifications/etc to provide predictable ordering
• Add LICENCE and README.MD to redistributable.