Wrap thead around 1st row, when 1st cell at 1st row is tableheader. Implements FS#1764
add <THEAD> to top rows of tables when all cells are <TH>
update tests for use with <THEAD> changes
swap order ot test parameters to match expected,actual as per documentation & test output
Merge pull request #390 from splitbrain/tablethead_chris

multi-row THEAD & tests
Merge branch 'master' into tablethead
implement rules for when the top rows of a table qualify for a THEAD element
1. TD < 2 in a row
2. TD <= 50% of total cells
3. Not all table rows can be THEAD rows
update unittests for THEAD rules
Merge pull request #387 from splitbrain/tablethead

Adding <thead> to tables