JSON Key Support

[sourcekris]

It is uncommon but I saw a CTF or two distribute keys as JSON blobs.

something like:

{'n':'0x1234....', 'e':'0x123'} 

The text key parser is already overly complicated with regex matching. I don't really want to write an AST based key parser either. So perhaps a first pass at this with -json boolean flag where users can self identify the key is JSON.

The default should be false.

It should support lists / slices of keys and when a slice of keys is found it could act as in the -keylist flag.