Migration from 0.93 to 0.94

1. MyPageKit has been replaced with MyPageKit::Model.

To update rename MyPageKit to MyPageKit::Model and rename
auth_credential and auth_session_key to pkit_auth_credential and
pkit_session_credential.  Modify methods to take $model as
first argument instead of $pk.

Also, replace handler with pkit_dbi_connect, pkit_session_setup,
and pkit_common_code.  See the code in eg/Model/MyPageKit/Common.pm
for an example of how to do this.

