Adding function strsplitsep to common.c and common.h file

This funcion is very similar to strsplit funcion, but admits a customized field
separator
Adding feature to customize IPMI sensors name

These feature allows the user to add a customized name for the IPMI sensor.
Next to a sensor name, insert the customized sensor name as follows:

Sensor "Real Sensor Name;Custom Sensor Name"
Taking away some test comments
cleaning code a bit more
Working version of ipmi with default sensor names

Please note:
* I had to do some nasty things to file src/utils_format_graphite.c to make
everything work with a compliant sensor name. This MUST be changed in future
versions
undoing one dirty change
Adding 'IgnoreSensorFail' option so that sensors are not removed

If option 'IgnoreSensorFail' is set to true, then sensors are not removed when
one single reading fails. Default value is false.
Renaming customname to custom_name
Minor cosmetic changes in syntax and whitespace