Fix bug that caused footer cache entry to have invalid modification time.
Make sure the cache has at least a minimize size.
wqAdd some basic unit tests for FootersCacheEntry. Fix missing new line at end of TestLruCache.java. Update FootersCacheEntry.getFooter() to simply return the footer instance variable.

Conflicts:
	parquet-hadoop/src/test/java/parquet/hadoop/TestInputFormat.java