Kubeconfig merge was completely rewritten to be "smarter":
* automatically apply renames done at previous stages to avoid asking
over and over again (in general should ask just once)
* skip checks if parts of the config match exactly
* allow overwrite as an option
* flexible way to control the output
* activating context in the end
* custom merged context name
Fixes#2578Fixes#2587Fixes#2577
Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>
