[BUGFIX] Allow upload of files without file extension

This change allows upload of files without a file extension. The upload
of PHP-Files is still not allowed. The method importUploadedResource
does not have a unit test, since it is not testable through the use of
move_uploaded_file.

Change-Id: I3a0a6ad89ab876a1c2113b0b6db967f983f5ef41
Resolves: #46536
Releases: master, 2.0
Merge remote-tracking branch 'upstream/master'