Refinements of Array macros.

Given a little encouragement everything seems to be inlining such
that the various methods in sandbox/array.scala are generating
near-optimally.

I guess this command line isn't much use to anyone but me but for
my own reference, this is how I inspected:

m7scalac -Xprint:typer -optimise -cp $(find $(fname scala-2.11.0-M7) -name '*.jar' | mkString :) -d sandbox sandbox/array.scala \
  && m7scala -cp $(find $(fname scala-2.11.0-M7) -name '*.jar' | mkString :):sandbox
Remove ScalaTest 2.0 deprecations
Add basic collection implementation sniff tests
Conciseify JsonVariant tree construction macros
Compact JsonVariant and BsonVariant factory methods
Consolidate Variant interfaces