Fix OAB TWR and DeltaV calculations if celestial body is changed in the stock dv tool - reported by @Deadly_Laser
Explanation of the solution: if another body is selected in the game's dv tool, then Micro Engineer's body dropdown will be locked to that selected body. If body in the game's dv tool is switched back to Kerbin, then Micro Engineer's body dropdown will be unlocked too.
OAB stages now keep their selected body - requested by @adaniel87
Note: this update can take a while, up to a few seconds - no need to report this.