RELEASED: Public: 2012-07-31
Add support for checksums:
The update center metadata now supports sha1 sums of core and plugin downloads.
Where the core/plugin is sourced from an upstream source that provides the sha1 sum then the download will only be accepted if the sha1 matches.
There the core/plugin is sourced from a source that omits the sha1 sum then the download will be assumed to be valid and the sha1 will be generated at that point so that any downstream sources will be able to validate the sha1.