DS-1559 Empty dc fields causes page layout issues

Fixing a number of issues caused by empty metadata fields in Mirage
Delete flexjson, use only google json
Changed name to linear workflow phase one (collision with linear workflow in bte.xml)
Merge branch 'master' of https://github.com/DSpace/DSpace into DS-1252-bte
Merge Spring XMLs for BTE services (batch import and submission lookup) to avoid duplicate beans declarations
merge with ekt branch
add missing images for new providers in the submission lookup process
Merge pull request #9 from lap82/DS-1252-bte

Move serialize/deserialize json to use google gson library, and remove abandoned code
resolve problem with referencing old class
Cleaned code and refactoring
Merge pull request #10 from lap82/DS-1252-bte

Cleaned code and refactoring
Code formatted with DSpace conventions
Merge pull request #11 from lap82/DS-1252-bte

Code formatted with DSpace conventions
The temp file is now unique and the file is correctly deleted

The temporary file is created using the File.createTempFile method to
avoid the potential overwriting if more than one users try to upload a
file simultaneously. Also the file is now deleted in a finally clause
to delete it even if an exception is thrown.
Use properties files for map converters
Merge branch 'DS-1252-bugs' of https://github.com/EKT/DSpace into DS-1252-bugs
Added specific configuration file for submission lookup
Merge branch 'DS-1252-bugs' of https://github.com/EKT/DSpace into DS-1252-bte
Some minor changes, fix retrieve data from crossref response
Merge pull request #12 from lap82/DS-1252-bte

 Some minor changes, fix retrieve data from crossref response