Implemented support for detection and skipping of duplicated photos

Using the experimental/instagramIds endpoint the upload-eyeem-pic.php check if the photo already exists on EyeEm. If exists skip it!

*** There must be something wrong with the endpoint I guess. It only returns 32bit integer for keys (Instagram ID), but they should be 64bit integer. ***

User should be informed that duplicated photos are not imported. This feature in the UI/UX have to be implemented ASAP.

Signed-off-by: Simone Conti <s.conti@itnok.com>