Currently we are handling conversion in the simplest way, by
just parsing protobuf text format representation of pb message,
splitting string in half and storing values wrapped in ""-s
in python dict. Which leads to a bunch of errors, like,
for example, when converting bytes fields. It also doesn't
handle types properly.

This patch introduces a proper way to handle pb<->json conversion
by iterating through pb fields and properly storing them in dict
or properly extracting values from dict.
Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>