migrate old what tags to unit tags, new use for what tags
make ES index configurable
allow graphite to slack a little more

also don't check for len, that's resolution dependent
check check result against most recent

this fixes an issue where it would keep sending the same alerts
over and over
include wtforms for nicer validation and form generation
add bootbox dep
give alerting some love

* implement edit/delete backend and views for alerts, using wtforms
* implement validation
* allow alias and "active" setting for alerts