Email Alerts, Job Scheduler with Variables

Webinterface can now send emails when ffastrans was not reachable. On slow systems, make sure the API timeout is high enough so it does not to spam your inbox.

Job Scheduler can finally also submit variables to the jobs which makes it a lot more flexible. The Interface has changed but it should be backward compatible to any existing scheduled jobs.

As usual other small enhancements and bugfixes e.g:
-) metrics: configure prometheus data retention days

-) log viewer: apply filter_job_status_buttons if any

-) job viewer: fixed incoming jobs not being displayed at all
-) job viewer: better display of sorting order
-) job viewer: icon for columns where filter is active
-) job viewer: always sort by date on page load so sorting is not stored/restored anymore