simplify subscribersSummary implementation
make date/time format configurable
Display clients with no subscriptions
Merge pull request #104 from palourde/issue-98_0-subscriptions

Display clients with no subscriptions
Merge branch 'feature/date-format' of https://github.com/ayan4m1/uchiwa into ayan4m1-feature/date-format
Fix subscribersSummary() unit test
Merge branch 'ayan4m1-feature/date-format'