Misc fixes to ACLReportTools and Documentation Update

1. Added DiffType to ACLReportTools.PermissionDiff table view format.
2. Updated readme.md with full details of ACLReportTools
3. Misc bug fixes to Compare-ACLShareReports
4. Added Import-ACLShareReports and Export-ACLShareReports cmdlets.
5. Corrected/updated/added cmdlet documentation.