Changes in this release:
- 1447acc webui: allow dash and underscore in topic names
- 4ce3bff send2mqtt: use unixtime for timestamp
- 9d11bc3 sysupgrade: automatically download gestalt when needed.
- 3d8d8fc better handling on empty values in numeric variables
- d89a489 utils: add tzselect cli app to select timezone. extract common code from gestalt and tzselect to common file.