plotman config validate

[JoshuaEstes]

I would like to be able to run plotman config validate and have it check the config file and let me know if the file contains any errors. Stuff like syntax errors, invalid directories and other invalid parameters would be helpful.

Right now I need to run plotman interactive and see if there are any errors. When I do it will kick off another job which isn't what I want sometimes.

So having a command that will check the syntax and contents of the config file would be helpful.