Fixes Issue #39 with other minor improvement.

[HalideGlow]

Addresses issue #39:

• Fixed swapped variables: mqtt_retain and mqtt_topic in entry.sh.
• Changed mqtt_retain from string to boolean under schema in config.json.
• Removed unnecessary "" around mqtt_retain value.

Minor Improvement:

• Updated logging to use bashio:log instead of echo. This will add formatting to log lines to make them look nicer. Example below.