Bit more checking on the params

[tttp]

Hi,

So I'm monkey testing civix, love it so far.

I am putting params that don't have the expected syntax, eg:
civix generate:page api_settings civicrm/admin/setting
civix generate:page eu.tttp.settings civicrm/admin/setting

and it more or less happily generate some files, but that aren't the right format so when testing further down got plenty of errors (eg because class name contains a .)

I'm sure it will be obvious soon what I can put or or, but in the discovery phase for noobs, bit of a pita.

Would be great to add some extra sanity checking, eg if the name of the page can only be [a-z]- add that test to avoid generating garbage.

X+

[totten]

Patched in 041a7dd