Static Index Pruning Tools
This package provides a framework for pruning an existing index into 
a smaller index while retaining visible search quality as much as possible.
An index can be pruned in several levels:
  - Remove stored data: see StorePruningPolicy
- Remove terms data: see TermPruningPolicy
Pruning can be applied programmatically via a 
PruningReader
or with the static tool 
PruningTool.