CI_ResponsibleParty as a responsible role attribute

Values are assigned according to table from CSW specification

| DC Metadata element name | Property mapping to ISO 19139 information model         |
|--------------------------|---------------------------------------------------------|
| creator                  | prefix[role.CI_RoleCode@codeListValue=’**originator**’] |
| publisher                | prefix[role.CI_RoleCode@codeListValue=’**publisher**’]  |
| contributor              | prefix[role.CI_RoleCode@codeListValue=’**author**’]     |
Merge pull request #169 from milokmet/pycsw263

CI_ResponsibleParty as a responsible role attribute