expose lib-Content modify/update Media function in javascript api

[ComLock]

Everytime metadata is changed on the FotoWare side, they change the image binary by writing the metadata into it. There I need to update the binary on the Enonic side quite often. Currently I have to use deleteAttachment and addAttachment, which does not update image metadata.

[sigdestad]

This functionality appears to be available in the Java layer, as it is already possible to upload new binaries to existing media, and metadata is automatically updated.