MQTT dynamic pulse timer for relays

[mcspr]

Resolves #816 (ticker revert) and #831 (/pulse/set)
Add {root}/relay/N/pulse/set setter to toggle relay for specified time.
Display pulse time and mode in terminal.

Overrides relay pulse settings and starts ticker with them. Resets to values from settings after starting.

[xoseperez]

Merged but I did some changes:

• Pulse payload in millis to allow under 1s pulses
• Added same functionality for HTTP API
• Topic set to pulse/+ instead of relay/+/pulse

[mcspr]

But it did use floats as an input - just like web does. Settings stored as floats too thus the conversion for getSetting. Subsecond values for web: 0.1s === 100ms

HTTP API is nice, yes 👍

[xoseperez]

You are right, do you think we should use the same units in web interface and mqtt/api

[mcspr]

Maybe just use ms everywhere? Gets rid of multiple divisions / multiplications and web would not require some clever hint to denote 0. value usage (it is obvious only if implementation is known beforehand)

I see that 74e27ee had already changed this.