delete tag before recreating it from svn (for svn tags that were updated since previous rebase)
update default options to be more reasonable

- verbose by default (because svn2git fails more often than not)
- metadata by default (--no-metadata is actually discouraged from use)
- remove phantom svn branches with @rev suffix (those are svn branches which were deleted and recreated)
- don't remove svn/ prefix when checking out remote/svn/branches (svn/ prefix is very useful for identifying branches imported from svn)