Support 'local' plugins

[kaidaguerre]

from https://steampipe.io/docs/develop/writing-plugins#writing-plugins

For example, consider a myplugin plugin that you have developed. To install it:

Create a subdirectory .steampipe/plugins/local/myplugin
Name your plugin binary myplugin.plugin, and copy it to .steampipe/plugins/local/myplugin/myplugin.plugin
Create a ~/.steampipe/config/myplugin.spc config file containing a connection definition that points to your plugin:
connection "myplugin" {
    plugin    = "local/myplugin"
}
Your connection will be loaded the next time Steampipe runs. If Steampipe is running service mode, you must restart it to load the connection.

however this does not work - we do not resolve local

[kaidaguerre]

this would resolve #1112