Change default value of `report-ttl` to 14 days

Most of our current UI mockups for future versions of PE guis
assume that we will have at least 14 days of report data around,
so we have decided to tweak the default value of this setting
accordingly.
Merge pull request #498 from cprice-puppet/maint/master/update-default-report-ttl-to-14d

Change default value of `report-ttl` to 14 days