Merge pull request #716 from akvo/issue/714_invalid_xml_characters

[#714] Escape predefined XML characters in survey group name
[#651] Enable counting of questions with *Allow Multiple* flag selected
[#643] Take into account variations in old style identifiers

* Check that the old style identifiers are at least 8 characters long
Merge pull request #721 from akvo/issue/651_data_summarisation

[#651] Re-enable counting of questions with *Allow Multiple* flag selected
Merge pull request #722 from akvo/issue/643_code_cleanup_monitoring_code

[#643] Take into account variations in old style identifiers
[#690] Fixes appengine-web.xml template

* The placeholders for key/secret are swapped!
Merge pull request #723 from akvo/issue/690_wrong_settings

[#690] Fixes appengine-web.xml template
[#725] Property signingKey is required

* The signingKey property is required for calculating and comparing the
  value in .sig file produced by the device
* Recover the option in the InstanceConfigurator
* Optimize the code for not executing the signature calculation if
  `allowUnsignedData` is true
Merge pull request #726 from akvo/issue/725_signingKey

[#725] Property signingKey is required
[#725] Fixes optimization logic

* We want to only calculate the signature if `allowUnsignedData` is
  false
* We need to check if we have a .sig to compare to and, if we have
  actual data to calculate the signature on. If one of those is
  missing we throw an Exception.
Merge pull request #729 from akvo/issue/725

[#725] Fixes optimization logic
[#733] RELEASE NOTES v1.7.2
Merge pull request #734 from akvo/issue/733_release_notes

[#733] RELEASE NOTES v1.7.2
Merge branch 'release/1.7.2'
Merge branch 'master' into develop