* new platform api, chassis part
* Inject mlnx mlx libs to platform monitor
* address the review comments
* remove some confusing naming.
* Adjust the minor cause to a more human-readable way when rebooted by firmware
* address review comments
* expose host dir /host/reboot-cause to pmon docker so that the reboot causing by user command can be identified
* 1. Revert "expose host dir /host/reboot-cause to pmon docker so that the reboot causing by user command can be identified"
Since the only hardware-causing reboot should be handled by get_reboot_cause and the logic of handling reboot cause is about to move to the host side, no need to mount this dir to pmon docker.
This reverts commit 3feb96869d.
2. adjust log output by using sonic_daemon_base.daemon_base.Logger.
3. remove the logic of verifying /host/reboot-cause/ files.
4. fix typo.
* implement get_firmware_version and adjust the interfaces regarding components' version retrieving according to the Azure/sonic-platform-common#34
