Yet another sharding support implementation

[clslrns]

This one is inspired by #691.

Brief summary:

• shardKey property was added to ClassMetadataInfo, mapping support were added to all drivers. It's a hash with keys and options. keys was originally called fields, but I decided to conform to the indexes definition.
• shardKey is class-based, since we need to keep the order of the keys to ensure compound index.
• ensureSharding method were added to SchemaManager. It's similar to ensureIndex. For non-empty collections it will run ensureIndex and retry shardCollection again.
• DocumentPersister uses shardKey to generate query part for upsert, update, remove, findOne.

I tried to cover all the new code with both unit and functional tests. Tests were run against sharded clusters of MongoDB 2.2.3, 2.4.9 and 2.6.5. Functional tests were tagged to avoid running against non-sharded setup.

Now I'm testing it on production. I'd like to receive some feedback from you guys to improve or change something.

[clslrns]

It seems, tests failed because of long MongoDB initialization. Would be great if somebody re-ran them.

[jmikola]

@clslrns: I will attempt to get to this before the next beta tag.

[clslrns]

Btw, wouldn't it be better to squash all this commits?

[notrix]

👍

[alcaeus]

@clslrns sorry for the long time without updates. Could you please rebase the branch to see if it still works against the current master?

One more note:

Btw, wouldn't it be better to squash all this commits?

Leave them as is - we can always talk about squashing commits before merging. For now this preserves important history.

[alcaeus]

I'm afraid this is a BC break. As useless as the ID parameter has become, it has to stay. Feel free to deprecate it though.

[clslrns]

@alcaeus, thanks for the feedback.
I have rebased it and fixed two issues you pointed to. I hope, in a few days I'll test rebased version against the app.

[darceee2]

👍

[alcaeus]

Superseded by #1385.