There was a missing image reload signal in node creation by drag-dropping,
which lead to incorrectly set image type.
Also fixed misusage of IMB_freeImBuf used to release buffer acquired by
BKE_image_acquire_ibuf.
Cutting mulitple links with for inserting reroute nodes would previously insert only one reroute node for the first cut link.
Now the operator will insert a reroute node for every link in the cut line. Also, if several links share the same input/output socket, it will insert only a single reroute node, which all affected links will then share.
Note: While renaming DNA properties is usually dangerous and can break files, in this case it is possible because the mx/my values are only used at runtime.
