fixes #5183 - Rename Systems to Content Hosts throughout the UI
Merge pull request #3984 from bbuckingham/system-ui-rename

fixes #5183 - UI - Rename 'System' to 'Content Host'
fixes #5232 - System Groups UI - fix link from system count to the group's System list.

Minor change so that clicking on the system count from the System Groups
list will take the user to the group's System list.