Make message db app use symbolic constants - initially STRINGs, but we'll convert to INTEGERs next time round.
Various refinements on AOM_PROFILE_DIALOG.
Convert all error message calls to using constants, so that in future no codes can be missed, since if they are, the system will now fail to compile.
Correct a dozen or so lurking error message errors, found by the new approach where error message codes are now constants in a dedicated class.