(PUP-2178) Map INI name to yumrepo descr

The yumrepo type uses 'name' as the namevar, while yum configuration
uses 'name' as the repository description. Because of this mismatch the
yumrepo type has a descr field that we need to explicitly map to the
'name' INI property. This commit adds the necessary mapping of that
field.
(maint) Yumrepo boolean values are case insensitive.

When handling boolean values for yum repos, a given value is downcased
before it is checked:

    # yum/config.py
    def parse(self, s):
        """Parse a string containing a boolean value.  1, yes, and
        true will evaluate to True; and 0, no, and false will evaluate
        to False.  Case is ignored.

        :param s: the string containing the boolean value
        :return: the boolean value contained in *s*
        :raises: :class:`ValueError` if there is an error in parsing
           the boolean value
        """
        s = s.lower()
        if s in ('0', 'no', 'false'):
            return False
        elif s in ('1', 'yes', 'true'):
            return True
        else:
            raise ValueError('invalid boolean value')

When validating these parameters we should perform a case insensitive
match to match the yum behavior.