coverity#707458 Uncaught exception (better fix)

getStatementsGraph_NoLock() cannot throw the exception because of the
i_Internal=true parameter, which may confuse Converity; but possibly
xIter->nextElement() could throw this in a multi-threaded scenario...

Change-Id: I204c0e5b38fee919d6cfe9247bde76b6ea78ed0f
oox: refactor embedded media import

Currently the oox import creates a temp file and leaks it, and there is
no way to clean it up afterwards.  Unfortunately it turns out that
SdrModel has no way to access the imported OOXML storage, so add a
really ugly hack to get the embedded media into the SdrMediaObj by
setting both MediaURL and PrivateStream properties (currently oox really
wants to set the properties in alphabetical order too...)

Change-Id: I5a235fbeb08e7bc17faf066de52b94867e9a79a2