ipagroup: Properly support IPA versions 4.6 and RHEL-7

group_add_member is only supporting services in more recent IPA versions.
This is 4.7+. Code has been added to detect if services are supported by
the used IPA version and used in the parameters of the module. In this case
an error is printed.

Additionally all parameters will be get from the module using
module_params_get provided by ansible_freeipa_module. Additional to_text
conversions have been removed as they are not needed anymore with this.