LUCENE-1288: add getVersion, getGeneration to IndexCommit

Files:
modified: /lucene/java/trunk/src/java/org/apache/lucene/index/DirectoryIndexReader.java (try)
modified: /lucene/java/trunk/src/java/org/apache/lucene/index/IndexCommit.java (try)
modified: /lucene/java/trunk/src/test/org/apache/lucene/index/TestDeletionPolicy.java (try)
modified: /lucene/java/trunk/src/java/org/apache/lucene/index/SnapshotDeletionPolicy.java (try)
modified: /lucene/java/trunk/CHANGES.txt (try)
modified: /lucene/java/trunk/src/java/org/apache/lucene/index/IndexFileDeleter.java (try)