Merge branch 'feature/deep_sleep_wakeup_from_touch' into 'master'

Merge branch 'feature/deep_sleep_wakeup_from_touch' into 'master'

add wakeup from touch sensor, and deep sleep example

- add new deep sleep wakeup mode
- change documentation to explain incompatibilities between different wakeup mode, add error checks
- add new ULP instructions necessary for ULP wakeup scenario
- fix issues with I_WR_REG, I_SLEEP, I_END instructions
- add deep sleep example, illustrating the use of timer, gpio, touch, and ULP wakeup triggers

See merge request !461