Support for application/x-base64-frpc in python handlers

[komackaj]

I've just found out that at least Flask handler in python/fastrpc/handler/flask.py - probably the other two are affected too - doesn't support base64-encoded data (Content-Type :application/x-base64-frpc).

IMHO it should

• detect encoded data from header
• automatically decode it
• encode output to base64
• reply with corect ContentType header

[ondras]

• encode output to base64

• reply with corect ContentType header

Ideally, the output encoding shall be driven by the Accept request header (as opposed to Content-Type. A client implementation can, in theory, send base64 but accept binary.