write pdf files
serpentine error removed
further major changes
Revert "further major changes"

This reverts commit 688081771ea7f6a55beb08727e56d7dbdd20e014.
changes
Merge branch 'version0.8' of https://github.com/GreatDevelopers/bakaplan
Documentation
DOc
Registration message changed
login link removed
Merge with version0.8 branch