nsqadmin: use go:embed; match graphite key valid charset

[jehiah]

This updates nsqadmin to query graphite using the correct key names for ephemeral topics and channels (see #1346)

[ploxiln]

interesting related PR for original statsd: statsd/statsd#155

[mreiferson]

OK, this also addresses #1317

[mreiferson]

heh, now the build pipeline requires the previously temporary static/build output files - perhaps we just check them in, so we can see exactly what the inputs are for a given commit?

[mreiferson]

also, lost "debug mode" from go-bindata, probably something we'll need to reimplement

[ploxiln]

now the build pipeline requires the previously temporary static/build output files - perhaps we just check them in

Yeah, I think we should. It shouldn't be too much, in fact it should be equivalent to bindata.go but a bit nicer. (Otherwise one has to install the npm dep tree and do the js build, just to build and test some changes to the go code, if using go-1.16+)

[mreiferson]

OK, think that should do it, PTAL!