Explores all sub-commands from root and adds a RunE for all
commands that are groups with child commands and without a RunE.
The added RunE will return the correct errors when the command
is called with empty sub-command or with an unknown sub-command.
It will also print the command help message first.
Added a gotest.tools test for root.go.
* Remove unused `--config` option
Currently `--config` option in kn command is not used from anywhere.
This patch removes the option from the command.
* update auto gen files
* Update deps by hack/update-deps.sh
Also:
1. New docs for commands
* service get
* revision get
2. Removes auto generated docs tags
3. Auto run generated docs when building to pick up any command changes