code: public static String getBuildString() {
  		String versionString = "UNKNOWN";
  		Properties propeties = getProperites();
  		if(propeties != null) {
  			versionString = propeties.getProperty("finmath-lib.build");
  		}
  		return versionString;
  	}
docs: Return the build string of this instance of finmath-lib.
  Currently this is the Git commit hash.
  
  @return The build string of this instance of finmath-lib.