Merge pull request #257 from vaibhavcisin274/vaibhav

Vaibhav
improving functionality of log_project_work_time
Merge branch 'master' of github.com:vaibhavcisin274/invoice-project into anshul
Merge pull request #258 from vaibhavcisin274/anshul

Anshul
invoice module implement all calculation functionality
Merge branch 'master' of github.com:vaibhavcisin274/invoice-project