EPIC: Implement Improved Pattern Metadata Parsing

[bmuenzenmeyer]

Implement the following per pattern-lab/the-spec#16

• parse state out of a pattern's .md Front Matter and map to a pattern's patternState proprerty
• remove setPatternState() from pattern_assembler
• parse order out of a pattern's .md Front Matter and use to override any file order prior to rendering
• parse title out of a pattern's .md Front Matter and use to override the filename
• parse additional keys ouf of a pattern's .md Front Matter
• display additional keys inside {{patternDescAdditions}} -- moved to ExtraOutput in data
• parse hidden out of a pattern's .md Front Matter and use to hide pattern from all direct individual or subtype rendering similar to _underscoredPattern.mustache today. These patterns should still be include-able as partials
• parse excludeFromStyleguide noviewall (or a better name) out of a pattern's .md Front Matter and use to omit pattern from all rendering
• parse tags out of a pattern's .md Front Matter and ... ??? (available in a future search enhancement?)
• parse links out of a pattern's .md Front Matter and display in a future are of the front-end
• unit test coverage