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
Port: new Mutable classes

MutableValueBool, MutableValueLong, MutableValueDate
Port: NumericUtils
Port: MutableValueInt, MutableValueFloat
Port: OpenBitSet
Merge remote-tracking branch 'jamesblair/lucene_4_3_0' into lucene_4_3_0
Port: OpenBitSetDISI, OpenBitSetIterator
Port: MutableValueDouble, MutableValueStr
Port: Add PagedBytes, DataInput, DataOutput

Also ported IndexInput, IndexOutput
Merge remote-tracking branch 'jamesblair/lucene_4_3_0' into lucene_4_3_0
Port: Add PrintStreamInfoStream
Port: PriorityQueue
Port: Add recycling byte/int block allocators