Update copyright dates
Bump version for 2.2.7-dev
[#9793] Preserve keys in xPDOObject::getMany()

array_merge was recreating numeric keys in xPDOObject::_getRelatedObjectsByFK()
[#6271] Limit reserved class_key column to inherit="single"

This allows the use of a column called class_key in table objects that are not specified as STI (inherit="single")
Bump version for 2.2.7-pl release
Merge remote-tracking branch 'xpdo/develop' into develop