Distinguish the stable from the beta builds.
version.h: break the defines and reindent the file for better readability
build.bat: Add the Beta suffix for beta builds and drop revision number for stable builds.
installer: use the existent copyright string from version.h.
vsfilter_setup.iss: bring it up to date with mpc-hc's installer.
Remove the "Beta" suffix from the packages.

The non-stable builds' packages include the revision number so this is unneeded.