Periodical accumulated hours reports via email

[jaragunde]

Send an email to phpreport users, with a configurable periodicity, informing about their accumulated extra hours in the year.

• Who will receive the email? Those users who have accumulated extra hours above a certain trigger. This trigger value will be configurable.
• When will they receive the email? A task to check who will receive the emails and generate the reports will run with a configurable periodicity, e.g. every month.
  • When running this task, extra hours won't be calculated based on the current date. Instead, their "last task date" (#357) will be the base date for every user, otherwise data won't be accurate.
• What data will the email contain? At least, the amount of extra hours since the beginning of the year, which caused the trigger to raise, and a weekly evolution since the beginning of the year. The intention is to make the report useful so it doesn't look like spam.