Enable YAML file encryption

An experiment, which works quite nicely. Just using pycrypto and shared key.

It works by having an encrypted file with .eyaml extension. If the .yaml file does not exist or it exists but is older than the encrypted file, the .eyaml file is decrypted using a key stored in environment or a file in project folder. Then the yaml file is loaded as usual (it does not intercept loading itself). You can encrypt specific configuration file by useing provided tool in scripts/
I like that idea, too. I'm content to put that off for another PR, but I'll make a card for it.