Allow campaign levels to specify leadlimit

Currently there's no way to set the lead limit for campaigns. I changed the formatting of the fraglimit field to allow "fraglimit+leadlimit" to be specified. Additionally timelimit can now be set to "" if you don't wish to override it.

Examples of setting fraglimit after this patch: "30+10" means 30 fraglimit, 10 leadlimit. "30" means 30 fraglimit, default leadlimit. "+10" means default fraglimit, 10 leadlimit.