* website: migrate to new nav-data format
* website: clean up unused intro content
* website: remove deprecated sidebar_title from frontmatter
* website: add react-content to fix global style import issue
Currently when data is imported via `consul kv import` it overwrites
keys under the root key. Since `consul kv export` can retrieve data for
the given prefix, i.e. part of the KV tree, importing it under root may
be not what users want.
To mirror prefix behavior from export this PR adds prefix feature to the
import command that adds prefix to all keys that are imported.
