Introduce Big-IP F5 http monitor module

Based on the iControl API and and implemented by the bigsuds python library
- https://devcentral.f5.com/wiki/iControl.LocalLB__Monitor.ashx
- https://devcentral.f5.com/wiki/icontrol.Python-Bigsuds-Library.ashx

This module allows to create and configure a "monitor" which is used to check the availability of a pool (managed by the already included bigip_pool module.)

This specific modules handles 'http' monitors. The module was written to make it easy to base other monitor types on this module, by updating the needed parameters, and updating or adding a minimum of code.

Thanks to @mhite for reviewing big parts of this module.