Update performance metrics rake task and documentation

InfluxDB fails to compile (package "context") without Go 1.7

Grafana's tslint grunt task fails without the --force argument

@jacobvosmaer-gitlab These changes make it possible for me to get influxdb and grafana running, at least, but I question why we're building influxdb and grafana from source. We don't have any intention of making changes to them within gdk, do we? So we should be fine with a prebuilt install of the two?

assigned to @grzesiek

merged

mentioned in commit 275d08e6

resolved all discussions

Thanks @nick.thomas! Let's merge this then!

Speaking from memory at least one of the two had pre-compiled packages that assume they're unpacked in the root.

To be honest, the current thing is what I could get working the fastest at the time, not necessarily what's best for users. It'd be much nicer not to have to compile of course.