Some porting work on Lucene 4.3, broken!
More porting work, still broken.

Focusing on Utils namespace now first
More Util work
Finish CollectionUtil
Add CommandLineUtil
DocIdBitSet, DocIdSetIterator, Constants
Add DoubleBarrelLRUCache
Port: FieldCacheSanityChecker, FixedBitSet
Port: Add InfoStream, IntBlockPool

Mark IndexableBinaryStringTools as obsolete, move IdentityDictionary to
Support
Port: Add IntsRef
Port: add IOUtils
Port: Started Core.Util.Mutable namespace

added all classes for the Mutable namespace. MutableValue base class is
complete. Slight discrepancy with porting the public Java "exists" field
and "Exists()" method. not sure how to handle this properly. For now,
made protected _exists field and read-only Exists property
Port: Add LongsRef
Port: Minor change to MapOfSets

was "private final" in java
Port: Add MathUtil
Port: Remove MemoryModel
Port: Add IMutableBits
Port: MutableValueBool
Port: Incomplete work on SPI

Not sure if SPI is going to look like this in the .NET port, but I
started on the classes anyways. Also, fixed a dumb mistake in
IMutableBits
Port: Add NamedThreadFactory