GeneralizedTime, UTCTime refactoring and some bug fix

• Changes from 10.4.0 to 10.4.1 release
  • src/asn1.js
    • refactoring of DERUTCTime, DERGeneralizedTime and DERAbstractTime
    • now DERUTCTime support fraction of second
  • src/asn1x509.js
    • update Time class to follow DER{UTC,Generalized}Time update
  • tool/tool_tsreq.html
    • messageImprint bug fix (#504)
  • tool/tool_tsres.html
    • serialNumber bug fix (#505)
  • jsrsasign-*-min.js
    • header URL fix to kjur.github.io (#503)
      (will be fixed in next release while rebuild)
  • test/qunit-do-{asn1,asn1x509}.html updated
    • KJUR.asn1.DER{UTC,Generalized}Time, KJUR.asn1.x509.Time class
      test case added and updated.