Working login, pass change, wlan disable and icmp set

[mliezun]

Based on the python implementation found on this site: https://blog.hqcodeshop.fi/archives/259-Huawei-E5186-AJAX-API.html

Hi, i've closed the other PR to start fresh. Here is all rebased into a single commit.

Sorry for the inconvenience but i will need you to point out where i have to change the code to make it idiomatic go.

Thanks in advance.