Static configuration for LED & Buttons

[mcspr]

• use similar to relay & wifi, configuration through helper methods that use indexed defines
• clock cycles for led delay polling. less cpu time than millis, since we only ever use small delays.
  I wonder if polling is even necessary though and this can be system timer (through Ticker) with periodic re-scheduling of either ON or OFF digitalWrite callback.
• button mode defaults in the header. add RELAY_NONE, similar use-case as GPIO_NONE, removing - 1 for each relayID operation.
• cleanup some size() checks

This also changed Dual and Foxel initialization of buttons, since wiki states

The Sonoff Dual it's a bit tricky to flash since GPIO0 is not connected to the button

No reason to use real GPIO.

Small patch for #2116 to use a different style of enum.
Fix espurna-base build by having TimeLib.h in utils (since we do use it)