untested client code
mapfishapp - implementing #754

Adding the possibility to set the FileDescriptor's save file.
mapfishapp - file formats as JSON

Adding some methods to access the supported geo file formats (depends
whether or not OGR is available).
mapfishapp - fixing programming error

Avoid having to instantiate a daughter class to guess which file formats
are available, removing useless methods related to the available format
support (managed by another classes).
mapfishapp - using common access to supported geo formats
mapfishapp - upload / download geo file (#754)

First naïve implementation of the download feature, all the security is
based on the fact that only zip files and xml derivatives can be used as
geo files. This might deserve a better hardenning to avoid security
flaws, but should address the feature request for now.

This seems not really functional with geotools implementation, so it
might need a gdal/ogr-enabled mapfishapp.

Test: mainly manual, might need to improve / adapt test suite.
mapfishapp - adding 2 methods on UpLoadFileMgmt

If going through download file (instead of upload), we need extra
methods to set extra infos on the FileDescriptor object.
mapfishapp - download file feature request (#754)

Fixing last bugs on the implementation, adding extra checks and
reindenting the whole file.
mapfishapp - download file instead of upload (#754)

Fixing some issues revealed by runtime tests
- file instead of url as parameter name
- do not add zip file as geo file in the File Descriptor class
mapfishapp - upload / download geo file (#754)

- url and not file as parameter name actually
- better error message in case of invalid form received
fixed missing fields
fixed missing record id
XHR rather than form submission
Show loading indicator while file loads
Merge branch 'master' into issue754
Merge branch 'master' into issue754
a bit of refactoring
translations
Merge pull request #806 from georchestra/issue754

mapfishapp - implements the ability to download a remote file (#754)