Merge pull request #53 from saloni10/dirty

imports corrected and some other errors removed
Removed some extra lines
Merge pull request #58 from saloni10/dirty

TA/DA work
Documentation for Bills app
Documentation with coding standards checked
Documentation for prints App
Merge https://github.com/divyanshikathuria/LibreHatti into dirty
Documentation for prints and catalog app
Merge pull request #65 from saloni10/dirty

Customer imported
Merge pull request #59 from divyanshikathuria/dirty

Documentation