[context] Use OptionBool class for boolean parsing
[context] Use OptionBool class for boolean parsing

The same parser is used for both parts of libdnf.
Now both parts accept the same strings for boolean values.

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