Add full mode stdin parsing

[Gbury]

Also, take the opportunity to clean up the logic class interface. Should solve #200

Note that even with this patch, in order to parse stdin using alt-ergo's native format, one need to use the new parse_all function, because the parse_input function will still raise. That being said the parsing pipe (in the loop sub-library) will adequately switch modes as needed and should allow full stdin parsing for all languages (as long as there is an end of input from stdin).

cc @bclement-ocp