Proposal regarding pre-releases

[Gigablah]

For the special case of pre-releases with their own special catalogue number and/or packaging, we add them as a "reprint" of the parent album. The album display page does a comparison of the release dates (it already does this to determine "alternate printings") and if it's release prior, it changes the display to "pre-release of".

Also, I propose that "Add Reprint" be changed to "Add Child Album", since it's now used for more than just reprints (e.g. bootlegs, alternate printings).