[#121] Implement authenticated S3 GET requests

* Add basic structure for auth requests
* Rely on new properties (survey.properties)
[#121] Add PUT implementation

* Use PUT instead of POST multipart for file uploading
[#121] DRY - Extract getDate() function
[#121] Extract common io functionality
[#121] Retry if the upload fails
[#121] Move bucket dirs to ConstantUtil

* Add status code check after PUT
[#121] Make image objects public
[#121] Fix S3 authenticated requests

* Refactor hash creation to return raw hash
* Send Base64 MD5 file hash
* Clean up S3Api file
[#121] Update property names
[#121] Delete unused code
[#137] Delete zip file once the form is extracted
Merge branch 'develop' into issue/121 (#121)

Conflicts:
	app/src/main/java/org/akvo/flow/service/SurveyDownloadService.java
	app/src/main/java/org/akvo/flow/util/MultipartStream.java
Merge pull request #147 from akvo/issue/121

Issue/121
Merge pull request #150 from akvo/issue/149

[#149] Disable 'save' property in CheckBox views. Code reviewed and correct.
Merge branch 'master' into develop
[#121] Use AWS naming convention
[#151] Hotfix release changelog
[#153] Close Data point after form submission

* Bump version number
Merge pull request #156 from akvo/issue/137

Code reviewed
[#153] Do not allow multiple saved forms

* Automatically open saved forms from form list
* Update DB methods/queries