Use manifest name in cache file name instead of manifest URL hash

[SpaceWalkerRS]

• Each manifest location now has a name, that must be unique. If multiple manifest locations are added with the same name, an exception is thrown.
• This name is used in the cache file names of the versions manifest and the version metadata. This will make the file names easier to read than the current solution, which is to add the manifest URL hash to the file name.