Center document widget and top bar title together

[SubordinalBlue]

Update: as of 95c5527, PR is now "complete", but of course open for requested changes.

Just two commits so far, with commentary in each: first to clean up a tad; second to get centering math in agreement for both the DocumentWidget and the top bar title.

There is an issue, existing before this patch, of duplication of the logic for positioning the Hermes' DocumentWidget; addressing that remains for a further commit.

I wanted to open this PR now both for feedback on the centering changes and, to be open to advice on how to address the duplicated code.

Will add some test images in a further comment.

[SubordinalBlue]

Test images.

All are details from F2 screenshots inside a graphics editor to over-lay guide lines, etc.

Full width view, top portion of a quest screen with sidebar. The editor-added green boxes have equal pixel width (UI=4).

Tighter details, same layout, at different UI scales 5 to 1: 5	4	3	2	1

Details for the no-side-bar case look the same, with the guide line being at 960px on a 1920px-wide MC screen.

[SubordinalBlue]

Added two further commits:

• eb36683 for edits that shouldn't have "escaped" the previous commit, my bad.
• 95c5527 for consolidating duplicated content area calculations.

Further details in those commits' messages.

[ThatGravyBoat]

After conflict is fixed it can be merged 👍

[SubordinalBlue]

Fixed.