Include webodf-specified formatting properties by default

Every existing use of this function will return better data if the system
defaults are included.
Refactor how style summary is retrieved to use cached values

When selecting or modifying large areas of content, the multiple
style information lookup becomes quite expensive. These can be greatly
sped up by using a common cached value + associated query object
instead.
Merge pull request #328 from peitschie/style-summary-cache

Refactor how style summary is retrieved to use cached values