Publish some topics directly to topic levels

<server>/state is now published directly to the <sever> topic level (the "state" topic goes away).

Moved <bbs-id>/node# topics to <bbs-id>/nodes/# (allows better wild-card subscription per MQTT standards).
Publishing total node count to <bbs-id>/nodes rather than <bbs-id>/node_count

Introduced "publish verbosity" control (defaults to "High") - if you want nice human readable (and sometimes redundant) topic messages, leave this set to "High". To reduce traffic, set to "Low". It's expected that purpose-built Synchronet/MQTT clients should work equally-well with either setting, but when using generic MQTT clients/browser, "high" verbosity is nice. The human-readable node status is only published when "high" verbosity is enabled.

Publishing the BBS name to the <bbs-id> topic, the instance hostname (as configured in sbbs.ini) to the <host> topic. Makes the hierarchy much more clear when using an MQTT browser like MQTT Explorer.