Make Loki connection optional

[evansteelepdx]

Currently the Loki connection details are required as part of the startup process. Runtime errors can occur if

• The loki object in settings.json is not populated with all required keys
• The loki endpoint does not return a valid result in the query_loki method

Consider adding a check in the initialize function to verify that the keys in the loki object are populated. We'd also want to ensure that the default settings.json file is populated with the Loki configuration object to avoid the read errors when the settings file is read.