Write netsender client for Atlas Scientific conductivity (salinity) sensor

[Trek Hopton]

See https://bitbucket.org/ausocean/rig/issues/3/salinity-integration-of-atlas-scientific for related issue.

A netsender client should be written in golang to report the conductivity values obtained via i2c comms with a pi zero.

Reporting as a scalar integer pin has been done for a number of our sensors and this method can be used for this sensor too.

[Trek Hopton]

Resolved in PR #86