Issue #283 - Overhaul preferences layout

Fix preferences layout in order to avoid a text above a checkbox. Give
some padding to the screen to increase the readability.
Issue #283 - Fix scrolling bug in Settings screen

Some texts were leaving a trace while scrolling the list. Now the scroll
is smooth. Give some padding to the screen as well, to increase the
readability of the content.
Merge branch 'develop' into feature/appui
Issue #305 - Increase cache expiration to 12hrs
Merge branch 'feature/appui' into develop
Issue #305 - Create new index for remote_api processing
Issue #305 - Use Memcache to make processing lines more robust

* Since a query to QAS may not return a value that *does* exist
  in the datastore, we use Memcache service to store for 15min
  the combination of {surveyInstanceId, questionID}
* If we find that combination in the cache, we skip processing
  that line to avoid duplicates
Issue #313 - Hide advanced option "Include DB instructions"
Issue #314 - DATA delete actions are only allowed to ADMIN users

* Delete actions in data tab are only available to users with ADMIN
  level
* We hide the option from the UI but also secure the REST api
  intercepting DELETE calls to /survey_instances
Issue #312 - Small code fix to test RawDataExporter
Issue #267 - Use Double for exporting NUMBER questions

* Use the question defintion to check if the current string value
  is a NUMBER question
* Set the type for that cell to NUMERIC
* Use Double.valueOf for conversion
* NOTE: We need to be aware that decimal precision
  will be lost on that conversion
Issue 301 - Improve GPS accuracy and UI
deactivate unused services
Issue #306 - send and receive version from downloadService

Previously, we were only sending the version during the location beacon
events. But sometimes the download survey occurs first,
leading to the creation of a new device.
Issue #301 - strings for GPS accuracy changes
Issue #302 - fix bug in not showing 'next' button after delete
Issue #302 - change way row index is computed
Issue #211 - restore order of questionGroups in case something goes wrong
Issue #211 - restore order if things go wrong

Because of the high-replication datastore and possibly other
issues, sometimes the order of questions and question groups goes
wrong. Here, we check and correct it at each save.
Issue #211 - enable copying of questions across question groups