3.0: Replace gerrit.disableReverseDnsLookup with gerrit.enableReverseDnsLookup
3.0: Replace gerrit.disableReverseDnsLookup with gerrit.enableReverseDnsLookup

Also move the "Breaking Changes" section to a subsection of "Important Notes".

Change-Id: I4126828eeac685d0f128b361a88b4b23d7c13c3d

GerritCodeReview/homepage,GerritCodeReview/homepage,GerritCodeReview/homepage,GerritCodeReview/homepage,GerritCodeReview/homepage