Bug 933192 - [Settings] can join hidden wifi network without ssid name r=ejchen

a)target:prevent from joining hidden wifi network if any of the  fields are not valid:1)the ssid name2)the user name 3)the password
b)scheme:
three js files are modified during the process:shared/js/wifi_helper.js, apps/ftu/js/ui.js, apps/settings/js/wifi.js,
1)in shared/js/wifi_helper.js:
Parameter ssid is added in function isValidInput
2)apps/ftu/js/ui.js:
beside 'password' text,we also add event listener  to 'ssid' and 'user name' text boxes .the above three listeners could listen for any changes happened in the three text boxes and then disable or enable the join button
3)apps/settings/js/wifi.js:
beside 'password' text,we also add event listener  to 'ssid' text box .the above two listeners could listen for any changes happened in the two text boxes and then disable or enable the ok button

oh,I am so sorry to cause such a bug here.
I have tested the  WPA-PSK - SIM case here.but before test the WPA-PSK - SIM,I tested the WPA-PSK style and input the user name and password to enable the ok button.without click ok button ,I changed to the WPA-PSK - SIM,and the ok button is still enabled……
I  failed to carry a overall test .
I am sorry to bring you with such troubles,I 'll modify it soon.