zmNinja should give a useful warning when the API is non-functional

[bklang]

I tried pointing zmNinja at my default installation of Zoneminder. Everything appeared to work, but all the screens were blank and no monitors appeared. Using the instructions in the wiki, I checked to see if the API was working, which obviously it was not. This error should be detected by zmNinja so the user knows that he has work to do.

[pliablepixels]

Thanks for your contributions -always good to have someone who commits as well as comments :-)
You are right - in my euphoria of making API authentication work with ZM auth, looks like I mistakenly removed the API validity check. I'll add that back into LoginCtrl.js