[swig] ConfigParser: Improve compatibility with Python ConfigParser
[swig] ConfigParser: Improve compatibility with Python ConfigParser

Improve read method:
- accepts iterable of filenames
- returns list of successfully readed ini files

Added methods:
add_section(section)
read_string(string, source='<string>')
remove_section(section)
remove_option(section, option)
set(section, option, value)

rpm-software-management/libhif,hughsie/libhif,rpm-software-management/libdnf,rpm-software-management/libdnf,rpm-software-management/libhif,hughsie/libhif,rpm-software-management/libhif,rpm-software-management/libhif,rpm-software-management/libdnf,hughsie/libhif,rpm-software-management/libdnf,hughsie/libhif