Make auto-numbering more intuitive

From a user:

I am a community sports coach for orienteering in the NE and have managed to secure a very long term loan of EMIT kit from the importer but i have control codes that have gaps all over the range.

I placing controls with no courses defined. When i got to control number 184 and then went to 192 i expected it to then start incrementing beyond 192 but it keeps trying to add 185. I usually do it this way to keep the white course sequential

-- Should we adjust the algorithm for choosing new control numbers?