Allow server operators to set dropped CTF flag return time

[GooberRF]

This PR adds the $DF CTF Flag Return Time config item to dedicated_server.txt

This option allows the server operator to set the time after a flag is dropped before it automatically returns to base. If unset, the option defaults to 25000 ms (stock game value - ie. no change).

[is-this-c]

What about $DF CTF Flag Drop Time? Is it not a problem that players are not going to know what a server set it to? Is this feature needed?

[GooberRF]

Is it not a problem that players are not going to know what a server set it to?

While I would prefer clients knew, clients already don't know many server details that they really ought to - kill limit, cap limit, spawn protection duration, global damage multiplier, amp damage multiplier, etc.

Clients should know about all of those things, and if ever a method exists for them to know them, this value should be added to that list as well.

What about $DF CTF Flag Drop Time?

From the POV of a general user, this seems less clear. As-is, the server operator sets the "return time" - it's only possible for the flag to return when it's dropped, so I really can't see any cause for confusion.

[rafalh]

I like the current name. I also don't see it as a big problem that players don't know it when joining the server. If you join a modded server you also don't know how it works but after playing for a bit you get to learn it. Having some commands or UI for that in some far future could be a good addition but I don't think it should block this change.

[rafalh]

Please solve one more comment and fix conflicts