Conversion: Handle shorthand CSS properties

Conversion: Fix bugs in the handling of shorthand CSS properties
such as font or border, which could cause some properties to
not be resolved correctly during conversion.
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pep8
pep8
pep8
Use shorthand properties for margin, border and padding
Merge branch 'normalize'

EPUB/AZX3 Output: Use shorthand forms for margin, padding and
border CSS properties

Conversion: Fix a bug that could cause incorrect border values to be
used when cascading, shorthand border CSS is present.