qa: Added SwModelTestBase::getXPathContent

Equivalent to assertXPathContent but returning the string.

Change-Id: I06ae4ba7c17db188af64d152b9c2807cc84535ce
sw/qa: Code refactor.

Change-Id: I552b5111901a2e1011a2bd0acaf0231dadd56614
fdo#70838: apply rotation transformations to DML anchor position

Used the same algorithm that we had for VML to update the position of
the DML anchor taking into account the rotation of the shape.

Complemented the unit test to check the values in the generated DML.

Change-Id: Ie0293c3cf4d1309fad58c0387f1589e69071fd9a
ooxml: Make SdtHelper grab bag more generic

Flexibilize the way the grab bag in SdtHelper works, enabling it to
store several children of SdtPr.

For every tag inside SdtPr, we enable the DomainMapper grab bag,
store the children properties there, and insert the full grab bag
inside the SdtHelper grab bag. In this way, the SdtHelper grab bag
becomes a Sequence of pairs "SdtPr token name" -> "Bag with children
tokens and values".

The first advantage of this implementation is that we can preserve
dataBinding sdt property plus another one of those supported; until
now the second property overwrote the first one in SdtHelper bag. In
further patches we will add support for other tags.

Some lines are incorrectly indented to make the purpose of this patch
more evident, and will be corrected in the next patch.

Change-Id: I0ec7be7b96dca455bbbeb03fc2fed230df04c52a
Fix indentation

Change-Id: I380138438171c009a953cfc8afb2cc13e1c1e6a6
ooxml: preserve text sdt property

Change-Id: I46b857298ae5d86fe6055efb86d046da48882e8a
ooxml: preserve rich text sdt controls

These controls don't have a special property, like for example
unformatted text controls have. So we use the id property as a
marker; we will grab-bag it together with other sdt properties and
use the existing mechanism to write the sdt block on export.

A grab bag that only contains an id property is for sure a rich text
control so we add it to the character props and not to the paragraph
props, like in the case of the unformatted text control.

Word doesn't allow us to write an empty <w:id/> tag, so we fill
it with a random number.

Finally, modified an existing unit test to add a rich text control and
check it is exported correctly.

Change-Id: If403a4a2393d4ee069a628645e364d21f104a859