Introduce FileObject#isUploadable for files about to be modified

When users want to edit metadata in the updater GUI, we ask the file
object whether it can be uploaded. However, in this case the file's
metadata is about to be changed, but not yet changed. So we need a way
to ask: *could* this file be uploaded if the metadata were changed?

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Avoid using the now-deprecated isUploadable(FilesCollection) method

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Changed metadata constitutes a change, even an uploadable one

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Allow uploading bogus new versions of unchanged files

There are projects advancing versions without any actual changes inside
the .jar file. We still need to support that use case, even if it
disagrees with the way ImageJ/Fiji themselves are developed.

This fixes https://github.com/imagej/imagej-updater/issues/9.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add regression test for the upload of bogus new versions

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'upload-metadata'

This topic branch allows uploading metadata-only changes (which also
includes a rename to a "new version").

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>