Merge pull request #2 from 10Pines/feature/json_api_for_time_entries

Feature/json api for time entries
Set focus to worked hours field
Initialize new time tracker with some default values
Changed logic to calculate default date. Doesn't take last month avg any more, now it's fixed to 6hs
Changed session timeout to 8 hours
Select most used project by last week range instead of last month
Fixed most used centro de costos and most used tipo de hora to order by count
Rest API
- Added total_hours_in_period
- Added batch requests
Merge remote-tracking branch 'remotes/origin/master' into feature/json_api_for_time_entries