Revision 198272

block-containers improved/fixed. The following features are implemented and testcases exist:
left, right, top, bottom, width, height, block-progression-dimension (partial), inline-progression-dimension (partial), borders, padding, indents, reference-orientation.
autoheight works only for in-flow BCs ATM.

start-indent calculation fixed: uses inherited value if rules in 5.3.2 don't apply.