New feature: vertical alignment for text frames: UI part

Add a new combobox to the Options tab page of Frame dialog,
which works with RES_TEXT_VERT_ADJUST attribute.

The combobox is placed to the right side of the dialog,
to follow ux-advise suggestion.

Change-Id: I47cec8e9dea748b8e9d23fc51cacbeec1c890a4e
New feature: vertical alignment for text frames: Layout part

- Introduce a new attribute (content position) for fly frames. Content
position specify the top-left corner of the content area (where
frame content can be placed). Add methods and members for invalidation.
- Extract content's height calculation from SwFlyFrm::Format()
to a funtction so we can use this inside SwFlyFrm::MakeContentPos.

Change-Id: I64abb70afb652ad5c11aa69b5ba12a85210e215b