Made formatting strings compatible with python 2.6

Also fixed styling according to pep8
Change log for #316 and code style tweaks.
Don't rename the config file if there is nothing to migrate from
Merge pull request #317 from parapente/master

Don't rename the config file if there is nothing to migrate from
Changelog for migration fix (#317)

Eventually, we should just remove the migration code. Not sure when, however.
Fix bug where a null value for lengthMS would crash an import. Added a fallback to parse the standard min:sec length field.
Merge pull request #319 from tima/beatport-ms

Fix bug where a null value for lengthMS would crash an import. Added a fallback to parse the standard min:sec length field.
changelog/thanks/style for #319