Introduced output contexts for more general handling of serialised content.
Simplified the instantiation of new serialisers when encountering different
region formats.
1 ||<20%|2-2)^> Cell 1 || Cell 2 ||
2 || '''Cell 3''' ||<#FF0000 width="15%"> ''Cell 4'' ||
3 4 || Not a table
5 || Also not a table
6 || Almost a table || ...
7 || A table, trailing space ||
8 9 ||<20%%name="value"> Bad separator ||
10 ||<20%xx-2> Strange attributes ||