Attempt to keep same team/player IDs when importing schedules/editing runs, add external IDs

[zoton2]

Something that must've been an oversight when I added support for it but only noticed now, if you import a schedule with an "external ID" set, we never attempt to keep the internal IDs for the teams/players even if they are identical. Some logic could be added to keep any IDs the same if the external ID for that run matches,

From my limited testing, this may also happens when you simply edit a run too?

[zoton2]

As an extension of this, adding an externalID to both teams and players should help this. Horaro would just have to be a hash based on information we have (similar to what I do already for the runs themselves if no external ID is found) although Oengus does have IDs that can be used for players at least.