Send healthchecks report to email

[milanmajchrak]

Excel Notes: Admin could email a healthcheck reports, he could write an email and send it
TODO:

1. Report from all healthchecks write into email (Copy classes: Report, Check, ReportInfo, maybe more) + tests?
2. Add a new cfg property healthecheck.last_n_days
3. Create email template healthcheck
4. Run healthcheck from /processes; e-mail will be parameter

[Kasinhou]

Linked PR: #853