[docx] activeX reference files (.bin) saved in InteropGrabBag and exported.

  The XInputStream for activeX.bin files is stored as the PropertyValue
  "OOXActiveXBin" into the "InteropGraBag"

  Added mxActiveXBinList object which holds XInputStreams for each
  activeX.bin from activeX folder.

  Added .bin files entry to respective acivex.xml's .rels file.

  Added Unit Test to test all .bin files are stores properly.

Reviewed on:
	https://gerrit.libreoffice.org/6679

Change-Id: I3a0e9462a6cc53d8cbb9c7d59ed24631d77d4d30
CppunitTest_sw_htmlexport: check for nullptr

I couldn't reproduce this one, but JBFaure says on IRC it helps in his
case.

Change-Id: Ib0a22996bdfc758326c4910b5b652f0772c08912