Prototyping improved lazy series
Propagate builders in frame operations, print frame using address sub-range
Add virtual frame, fix printing
Return mappings as KVP (struct) and optimize sorting
Virtual frame extensions and optimizations

 * Change parameters of GetRange (to match common pattern)
 * Add 'Init' operation to vector builder and use it to make
   'frame.Rows' optionally a lazy operation (for virtual frames)
 * Optimize slicing on 'frame.Rows.[a .. b]' and add 'GetSubrange'
   operation to the frame
 * Support laziness on the 'Select' series operation
 * Materialize series using the materialization operation
 * Support lots of things on virtual frames
Add virtual ordered index

This lets us create a series that is indexed by DateTimeOffset, but
uses a virtual vector storing the keys under the cover.
Merge pull request #237 from tpetricek/master

Revisit type conversions, fix documentation and filling bug
Added Select and SelectValues to Frame and the latter to Series, in service of #172
Simplify FrameModule map / mapValues
Trying to fix the type inference error on Travis CI
Fixed type inference error for F# 3.0
Two-way map operation, work on search in vector, support more virtual operations
Generalize ranges and support search by value on virtual vectors
WIP: Scan based filtering
Fixed ResampleUniform to work with Lookup.Exact for #210
Merge pull request #240 from BlueMountainCapital/GH172

Added Select and SelectValues to Frame and the latter to Series, in serv...
Merge pull request #243 from BlueMountainCapital/GH210

Fixed ResampleUniform to work with Lookup.Exact for #210
Change semantics of firstKey, lastKey per #244
Fix naming, make test compile
Merge changes