Don't allow time series names that start with underscore

[happymcplaksin]

Right now the Admin UI lets you submit points for a time series that starts with underscore. In IRC jvshahid said it shouldn't allow you to do that.

Also, when querying via the Admin UI it silently strips underscore from the beginning of the time series name. For example, this query:

select * from _simple

will return results from the time series named 'simple' as if you had typed:

select * from simple

To be clear, I stumbled on this issue in a roundabout way--I don't need time series names that start with underscore :)

Thank you!

[jvshahid]

Awesome. Thanks @happymcplaksin. I'll take a look at this very shortly.

[pauldix]

Should be at the API level. It should throw a 400 with an error message that you can't start a time series name with an underscore, which should then be shown in the admin UI.