Move Index and IndexStore implementations into Engine.

Move Index and IndexStore implementations into Engine.

Also move most of the related tests.

LocalIndex test is commented out, because relies on the infrastucture existing only in Server - virtual file system, mocks.
We need to move it into Engine or extract into a separate package.

This CL also removes Dart implementation of BTree.
We now use a different approach to implementing the index.


Bots are red after the previous CL, I hope that this one will fix at least some redness.

R=brianwilkerson@google.com
BUG=

Committed: https://code.google.com/p/dart/source/detail?r=37993

[Brian Wilkerson, 2014-07-03 21:06:33]

I'm not sure I like the idea of moving the virtual file system into engine,
which makes me wonder whether it is a good idea to move the index implementation
there. I'd rather that you held off on this until we've had a chance to design
the package structure, but it this is the only reasonable way to fix the bots,
then LGTM.

[Brian Wilkerson, 2014-07-03 21:06:46]

https://codereview.chromium.org/365193004/diff/1/pkg/analysis_server/pubspec....
File pkg/analysis_server/pubspec.yaml (right):

https://codereview.chromium.org/365193004/diff/1/pkg/analysis_server/pubspec....
pkg/analysis_server/pubspec.yaml:10: path:
/Users/scheglov/Source/Dart/dart/pkg/analyzer
This definitely needs to be backed out.

[scheglov, 2014-07-03 21:30:47]

Committed patchset #1 manually as r37993 (presubmit successful).