Topic split, move and join - problems and solutions

[Kaik]

These are problems which I have found during refactoring and solutions that are currently implemented.

Topics join - previously it was appending posts from origin topic to destination one by changing origin posts dates to be one minute older than the last post in destination topic which IMHO is kind of odd but since some might wish this kind of behavior I have added join strategy option where you can choose append or mix - where append works as described while mix just adds posts without changing any dates.

Topics split - this action worked by splitting topic into two and it was based on post ids - which IMHO is wrong since post ids in a topic does not have to be in order (join, move post actions) because posts in a topic are ordered only by post date split is now date based. Because the order in which posts are displayed can be changed by user and splitting can work only one way this might be confusing.

Topic move - works without any problems.

Apart from that, I have added few more options that might be useful. For example, each of those actions on a topic has a reason feature so email can be sent to topic creator - I do consider to add an option to send a reason as well to poster(s) - this could be adjustable (topic creator, posters or both)

Split action has destination forum option for the new topic. Join has an option to leave origin topic as shadow same as shadow topic feature in the move action.