Prefs migration improvements

- check if all parents of .gconf/apps/gnucash exist before attempting migration
- wrap guile parts in catch/throw handlers to prevent GnuCash from crashing
  if something goes wrong during the prefereces migration
- add more sanity checks and debugging information
- set flag after first successful migration to prevent future runs

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23291 57a11ea4-9604-0410-9ed3-97b8803252fd
Prefs migration: fix radiobutton prefs migration

It contained a bug that would set two radiobuttons active in one
radiogroup. This was only really visible in the backend, but
resulted in the wrong option to be highlighted (for example
autoledger register style instead of ledger)

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23292 57a11ea4-9604-0410-9ed3-97b8803252fd
Prefs migration: write xsl transform to migrate a pair of coordinates

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23293 57a11ea4-9604-0410-9ed3-97b8803252fd
Prefs migration: migrate ofx and aqbanking prefs if these options were enabled at build time

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23294 57a11ea4-9604-0410-9ed3-97b8803252fd
Prefs migration: improve messaging

Redirect all messages to trace file (or wherever logs are configured to go)
Reduce default output by playing with the log levels

git-svn-id: svn+ssh://svn.gnucash.org/repo/gnucash/trunk@23295 57a11ea4-9604-0410-9ed3-97b8803252fd