[bind10-dev] support map type in config data

[zhanglikun]

>I tried to use map type in config_data, but it doesn’t work very well.  Has
config module supported this type yet?  If not, do you plan to support it in
the 
>future?

I read the document provided by Jelte again(see the following link), and
find map type was planed to support.  But the problem  now is it isn't
supported properly, at least  isc/config/config_data/check_type() doesn't do
any check for map type.  Same problem to
isc/config/config_data/convert_type() provided by me.

https://bind10.isc.org/wiki/DataElementDesign