Use Ubuntu:18.04 to fix ESP32 python problem

• Using ubuntu:18.04 for Docker container, since ubuntu:latest can not fetch python for ESP32 anymore.
• CPP_EXTRA_FLAGS are now resetted.

Renamed parameter "sketch-name" to "sketch-names" to enable comma separated list

• Changed required-libraries from space to comma separated list.
• Renamed parameter sketch-name to sketch-names to enable comma separated list.
• Accept comma separated list for examples-exclude.
• Updated documentation.

UPDATED to the content of v.2.2.0, because using ubuntu:latest leads to ESP32 compiling errors now

Added semantic for example name All in examples-build-properties

• Added missing newline after print of "Install libraries $REQUIRED_LIBRARIES".
• Added semantic for example name All in examples-build-properties.

UPDATED to the content of v.2.2.0, because using ubuntu:latest leads to ESP32 compiling errors now

Renamed parameter libraries to required-libraries

• Renamed parameter libraries to required-libraries
• Renamed script.
• Script instead of action can be used in steps.
• Added parameter arduino-platform to enable specifying the version of the required platform.

UPDATED to the content of v.2.2.0, because using ubuntu:latest leads to ESP32 compiling errors now

Initial version

v1.0.0

Version v1.0.0