APPS-1779 Simple time submission

:koala:

This PR intends to add simple time submission functionality, so the agents can submit time log as a single number which represents how many minutes they spent on the ticket.

Translations are in https://github.com/zendesk/timetracking_app/pull/39

/cc @zendesk/quokka 

### REFERENCE
- [JIRA APPS-1779](https://zendesk.atlassian.net/browse/APPS-1779)

### SCREENSHOT

![z3npo_-_agent](https://cloud.githubusercontent.com/assets/1329716/3730246/b27f9452-16cc-11e4-88da-ee58f5960627.png)

### RISKS
- N/A