extractorapp - Improve mail templating system (#750)

Implements the possibility to add custom key/value pairs replacements in
the templating mail system.

Manually tested.

Conflicts:
	analytics/src/main/webapp/js/lib/external/ext
extractorapp - using ${language} instead of forcing a locale

Conflicts:
	analytics/src/main/webapp/js/lib/external/ext
extractorapp - mail templates missing translations

Adding 2 files for de / es translations of extra keywords
extractorapp - reindent
Extractorapp - fixing indent on Email.java class
Merge pull request #807 from georchestra/issue-750

extractorapp - Improve mail templating system