Lowered precedence of OR-operator (|) in CorpusQL.

Before, "great" | "very" "good" would parse as ("great" |
"very") "good"; now it is parsed as ("great") | ("very" "good"). To be
precise, the OR-operator now has lower precedence than the (implied)
sequence operator, but still higher than the "within" and "containing"
operators.
Made CorpusQueryLanguageParser.parse() throw ParseException.
Simplified Example a little bit.

Called CorpusQueryLanguageParser.parse() instead of instantiating it and
calling query().
Added Hits.window() method to get a HitsWindow.
Added package.html to queryParsers.lucene.helpers package.
Updated README.
Added javadoc directory to .gitignore.