Messages: update create-IdP/SP select-Org tooltips

Update the wording in the tooltips displayed next to Organization
selection on the IdP/SP registration page.
Merge pull request #180 from University-of-Auckland/develop-ui+tooltip-clarifications

UI and tooltip clarifications
Merge branch 'aaf-develop' into code-develop
Merge branch 'code-develop' into tuakiri-develop
Merge branch 'tuakiri-develop'