Minor context improvements.
Be consistent about the escape key.
Minor changes to drawing text.
Mention fourth component of vectors in note.
Small grammatical changes in textures page.
List wrapping options in same order as image.
Allow writing multi-line display math.

Add 's' ('.' matches newline) and 'U' (ungreedy matching) to regex flags
for the display math conversion. This allows display math to be written
on more than one line, which is sorely needed for all these matrices.
Use correct font for subscripts.
Fix matrix-matrix product examples.

In a couple places, elements were swizzled, making things a bit more
confusing for no reason. Also, it's clearer to colour the *columns* of
the second matrix since matmul is row-by-column.
Spelling and grammar in last five articles.