code: String checkVersion(String pluginName, String dependency, String requestedVersion, String availableVersion) {
  		if (null == availableVersion) {
  			return "Dependency " + dependency + " not found for " + pluginName + ", version " + requestedVersion +
  					" or higher needed.\n";
  		}
  		if (requestedVersion.startsWith(EXPR_START) || availableVersion.startsWith(EXPR_START)) {
  			return "";
  		}
  		Version requested = new Version(requestedVersion);
  		Version available = new Version(availableVersion);
  		if (requested.getMajor() != available.getMajor()) {
  			return "Dependency " + dependency + " is provided in a incompatible API version for plug-in " +
  					pluginName + ", which requests version " + requestedVersion +
  					", but version " + availableVersion + " supplied.\n";
  		}
  		if (requested.after(available)) {
  			return "Dependency " + dependency + " too old for " + pluginName + ", version " + requestedVersion +
  					" or higher needed, but version " + availableVersion + " supplied.\n";
  		}
  		return "";
  	}
docs: Check the version to assure it is allowed.
  
  @param pluginName plugin name which needs the dependency
  @param dependency dependency which needs to be verified
  @param requestedVersion requested/minimum version
  @param availableVersion available version
  @return version check problem or empty string when all is fine