Create ISSUE_TEMPLATE.md

An issue tempate dereived from anisbles template and adapted to odoo. Should help to get higher quality issue entries.

This sould be referenced at the firt line of CONTRIBUTING.md to obtain this cool hint on issues:

![image](https://cloud.githubusercontent.com/assets/7548295/3075790/bb711840-e393-11e3-8623-1729b85af23a.png)