Add Logger Function Within Celestial API Code

[magneticstain]

Currently, each log message generated by the Celestial API has the same format, but with some values added in-line with the message, e.g.:

error_log('could not parse config file :: [ SEV: CRIT ] :: [ FILENAME: '.$configFilename.' ]');

We should add a logger function/class that can be used globally within all libraries for logging functionality. It should accept:

• severity
• primary message
• additional data in the form of an associative (key-val) array