Fix version number verification to allow releases

The verification of version number in version.config required
pre-release label always. This fixes the bug and allows release versions.

CMakeLists.txt

@@ -30,7 +30,7 @@ endfunction()
 
 configure_file("version.config" "version.config" COPYONLY)
 file(READ version.config VERSION_CONFIG)
-set(VERSION_REGEX "version[\t ]*=[\t ]*([0-9]+\\.[0-9]+\\.*[0-9]*)([-]([a-z]+[0-9]*))?([-](dev))?\r?\nupdate_from_version[\t ]*=[\t ]*([0-9]+\\.[0-9]+\\.*[0-9]*([-]([a-z]+[0-9]*)))*(\r?\n)*$")
+set(VERSION_REGEX "version[\t ]*=[\t ]*([0-9]+\\.[0-9]+\\.*[0-9]*)([-]([a-z]+[0-9]*))?([-](dev))?\r?\nupdate_from_version[\t ]*=[\t ]*([0-9]+\\.[0-9]+\\.*[0-9]*([-]([a-z]+[0-9]*))?)*(\r?\n)*$")
 
 if (NOT (${VERSION_CONFIG} MATCHES ${VERSION_REGEX}))
   message(FATAL_ERROR "Cannot read version from version.config")