docs: elaborate Table feature analysis
acpt: add scenarios for Table.autofit get and set
tbl: add Table.autofit getter

* Fixed sequencing of w:tblPr/w:tblStyle child element, was defaulting
to unconditional append.
tbl: add Table.autofit setter
acpt: add scenarios for Cell.width
test: reorder fixtures in Describe_Cell
tbl: add _Cell.width getter
tbl: add _Cell.width setter
release: prepare v0.7.3 release