Issue #452 - Add allowExternalSources flag

* Define a new attribute for Question kind
* Display the option in the Dashboard - per question
* Include the flag in the xml Survey definition
Issue #452 - Disable 'externalSources' option for non-text questions
Issue #452 - Only send 'true' allowExternalSources flag
Merge branch 'develop' into feature/external_sources

Conflicts:
	Dashboard/app/js/lib/views/surveys/question-view.js
	Dashboard/app/js/templates/navSurveys/question-view.handlebars
	GAE/src/com/gallatinsystems/survey/domain/Question.java
	GAE/src/com/gallatinsystems/survey/domain/xml/Question.java
	GAE/src/locale/en.properties
	GAE/src/locale/ui-strings.properties
	GAE/src/org/waterforpeople/mapping/app/gwt/client/survey/QuestionDto.java
	GAE/src/org/waterforpeople/mapping/app/web/SurveyAssemblyServlet.java
[#793] Add external sources flag to the instance
[#793] Fix formatting

* Apply formatting to old (tab-based) changes
Merge pull request #796 from akvo/feature/external_sources

[#793] Add 'allow external sources' flag in Free text question definition