text_properties page improved
* properties reordered for better grouping and priority
* data and font_angle descriptions improved (noticeably about how to
center the block on the pivot).
* alignment: + applies to all columns
* Examples: Extrawide MathML string wrapped.
* See also improved: + xstring, label_properties, legend_properties,
latex & mathML page; - set, get (too general)
* History section created.
* <emphasis> replaced with <literal> for better readability.
* Other misc. styles improvements.
Change-Id: I95ac39a831e0be4c3f320e1246697be9c27378d2