Stations: Expose "show" attribute to the mobile app

Arduino inverts this flag and interprets it as “disabled” instead of
“connected”. This adds support for the disable attribute into the
change_stations function which just inverts the value back.
Mobile App: Fix device detection

Using all protected JSON broke my automatic device scanning/detection (uses /jo to get fwv and see if valid).

I have added a /jv which only shows the firmware, something that's shown on the home page anyways. 

This should be enough to fix my feature without compromising security.

Thanks!
Update pcf_8591_adj.py

Error correction, add DA output
Update pcf_8591_adj.html

Correct error. Function OK, Add da output.
Update pcf_8591_adj.py

enable log to file. final OK
Merge pull request #21 from martinpihrt/master

Updated PCF8591 plugin
Use limited options JSON reply when unauthenticated
Changed check_login function to be able to use it without redirecting.
Use helpers.py check_login
Merge pull request #20 from salbahra/master

Stations: Expose "show" attribute to the mobile app