Clean up headers in CommonSettings and InitialiseSettings

Remove obsolete stuff and actually say what the files are for.
Also remove human-readable vim instructions, since (to quote
MZMcBride) "it seems painfully unlikely that anyone would be
using vim, editing this file, and either care or not know about
this info."

Bug: 48492
Change-Id: Ic5b8996651e04be51b1c5dfd310a35ffb930cf7c