FastVectorHighlighter: FieldTermStack.TermInfo should provide term-weight

This patch contains:

• FieldTermStack.TermInfo has now a field TermInfo.weight (float), which holds the index-weight (IDF) of the corresponding term
• FieldPhraseList.WeightedPhraseInfo has now a field WeightedPhraseInfo.termsInfos (ArrayList<TermInfo>), which provides information about the contained terms within the corresponding phrase
• WeightedPhraseInfo.addIfNoOverlap() no longer dumps the second part of a hyphenated word (for example: social-economics)
• FieldQueryTest has been updated

Regarding test-cases:
TermInfo.toString() wasn't modified, thus, test-cases remain pretty much the same except the additional parameter for TermInfo-constructor.

This is the third (see LUCENE-4091, LUCENE-4107) patch aiming at the introduction of another method for weighting fragments (see LUCENE-3440).