Fix flipped border-bottom-right and border-bottom-left

[LeoniePhiline]

Fixes #307

This pull request:

• Adds Border radius wrong output when using explicit radii #307 as test case and fixes it.
• Adds another test case (for <first> <second> <third> / <first> <second> syntax) from MDN.
• Fixes a previously false-positive test, caused by consistently placing bottom-left (or start-end) before bottom-right (or end-end)
• Prevents future similar bugs and reduces confusion by consistently re-sorting bottom right before bottom left (matching CSS syntax) across the border radius module and tests.

A note about white space:
Some white space was inconsistent, but that was not meant to be subject of this PR. I accidentally committed the removal of spaces from otherwise empty lines, causing diff noise. With this accidental change, the post-merge code is more white-space-consistent, but nevertheless please let me know if I should revert these accidental white space changes.

[devongovett]

Thanks!