Merge most of the changes that recently made it to master.
This will be the last such merge operation and future commits will only cherry-pick fixes and targeted features.
Major fixes and features,
- reboot cause enhancement with more hardware reboot cause reporting
- fix reboot cause parsing issue with 201811 release
- fix get_change_event logic
- fix error message on missing sysfs entry by our plugins
- final piece of the platform refactors for fan and sensor reporting through the platform API
* Add boot0 support for the 7280CR3
* Add platform and plugins for 7280CR3
* Add port config for 7280CR3
* Add platform_reboot for 7280CR3
* Add support for 7280CR3-32D4 based on the 7280CR3-32P4
* Update arista driver submodules
- Introduce new 7280CR3-32P4
- Improve to the led plugin for OSFP
