Move nodes_path from SoloCommand to NodeConfigCommand
Refactor NodeConfigCommand#node_config
Upload only the needed node config and make the path configurable

Use `node_path` to specify the directory where node configuration json
files are stored. Default to "nodes" as earlier. It is worth noting that
`node_path` defaults to "/var/chef/nodes" on Chef versions before 11.6.0.
But as that directory should not exist, we will fallback to "nodes".

We now only upload the json for the cooked node.
Upload all node json files and configure them for chef-solo-search

Future chef-solo-search versions will use `nodes_path` when searching
nodes. So upload them all and set the configuration accordingly.
Merge pull request #248 from tmatilai/nodes_path

Fix node config attribute handling and make "nodes" directory path configurable

Fixes #247