Move Sensors from Web dashboard to it's own tab

[proddy]

I've moved Sensors from the Dashboard Data & Sensors to its own tab and changed 'dallas' to 'temperature' in the API. The reasons being

• eventually we should support more than just the Dallas DS18b20 sensors, like DHT11, DHT22, LM35, BME280, BMP180 etc
• in discussing with BBQKees we have ideas to extend Sensors with more types
• the Add Analog sensor button (which was a + in the table) was a bit odd and not consistent with the rest of the styling, with an explicit 'Add' button
• it keeps the code tidier

The change from 'dallassensor' to 'temperaturesensor' is a breaking change. Old MQTT topics would need to be removed and any HA pages updated. Also I expect any integrations that don't use MQTT Discovery like IOBroker would also need updating.

[proddy]

The new tab is in PR #1162

[proddy]

in dev11