Bug 801909: Add validation to externalfiles.

* Move to a real management command.
* Add tests for updating and validation.
* Add ability to specify file class in settings.
Update a bunch of calendars for 2014

Bug 913379 - Updated Czech holidays file

Bug 1005069 - Date not according to spec in Dutch holiday calendar

Bug 1002035 - Haiti Holidays Calendar

Bug 936885 - Hong Kong Holidays 2007-2014

Bug 1001483 - Addition of Ireland Public Holidays 2014 to 2021

Bug 1015838 - Updated holiday calendar for Japan

Bug 1011883 - Morocco Holidays over (without religious holidays)

Bug 988735 - Holiday calendar for South Africa 2013-2021

Bug 1013063 - India calendar not download. Message displayed "Calendar not found on Server"
Add O2 purchase link to Alcatel OTF E. Bug 1042500.
Bug 1043366 - Add Berlin office contact links
Merge pull request #2175 from craigcook/bug-1043366-berlin-office-links

Bug 1043366 - Add Berlin office contact links
Merge pull request #2169 from kewisch/holidays

Update a bunch of calendars for 2014
Merge pull request #2174 from jpetto/bug-1042500-add-de-o2-link-alcatel-otf-e

Add O2 purchase link to Alcatel OTF E. Bug 1042500.
Merge pull request #2164 from pmclanahan/fix-credits-missing-500-801909

Bug 801909: Add validation to externalfiles.