Fixes #6081 - Add Gatwick (EGKK) split GMC position

[chssn]

Fixes #6081

Summary of changes

• Amended EGKK_GND to EGKK_S_GND and short code to KKGS
• Added EGKK_N_GND with freq 121.540 and short code KKG

Used LL Sector_Ownership.txt as the reference for the following changes

• Added KKGS into SECTOR OWNER
• Amended KKGND to KKGND_S and set KKGND_N as BORDER
• Added new SECTOR for KKGND_N and set KKGND_S as BORDER
• Set upper limit to 200ft as per LL GMC positions

[chssn]

Hang on... just sorting the sector boundaries

[Liaely]

Whilst I appreciate the enthusiasm, please can you not define separate GMC boundaries like Heathrow?
Given the simple nature of the split, we will not be including it in the sector file.

Also, in the future, it would be appreciated if you didn't request a review, at least on my part. Thanks!

[chssn]

Ah, the reason for the sector boundaries was due to the sector file compile error on the first commit. I'll remove the boundary reference which should get it past.

Only picked you as you'd generated the issue but noted!