Fix authentication issue

[Exhar]

Rewrite code to use user.authenticate instead of user.login (which is deprecated since 1.8). Verified to be working with Zabbix 4.0.0rc3

fixes #1

[Exhar]

fixes #6

[sdalmolin]

HI all,

A have a same problem, btu in another screen error.
zabbix: 4.4
php: 5.4

When access the zabirepo in chrome this under error :

Response Data Error / Response Code: 200 / Response Text: {"jsonrpc":"2.0","error":{"code":-32602,"message":"Invalid params.","data":"Invalid parameter "/": unexpected parameter "extendoutput"."},"id":1}