DOCS-2473: sharded collections' indexes cannot cover queries; refactor covered queries

Signed-off-by: kay <kay.kim@10gen.com>
tweak wording
DOCS-3995: Explain how sparse indexes interact with null queries.

Signed-off-by: kay <kay.kim@10gen.com>
switch sentence order
DOCS-3561 - added important callout for mongorestore and users existing in dumps

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-3561: edit
DOCS-3443 - clarification re: user for db.copyDatabase() with --auth

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-344: edit to verbs
mongoimport --drop does not drop all the collections

For example in 2.6.4

If you specify the collection it will only drop that.
```$ mongoimport -d test2 -c test --drop test.js
connected to: 127.0.0.1
2014-09-22T16:44:01.692+0100 dropping: test2.test
2014-09-22T16:44:01.715+0100 imported 1 objects
```

If you don't specify it. It will only drop the collection with the same name as the file you're importing.
```
$mongoimport -d test2 --drop test.js
connected to: 127.0.0.1
no collection specified!
using filename 'test' as collection.
2014-09-22T16:44:32.534+0100 dropping: test2.test
2014-09-22T16:44:32.537+0100 imported 1 objects
```

Signed-off-by: Sam Kleinman <samk@10gen.com>
Be more precise about in-memory sorting limit

I asked kernel engineering what exactly the size limit for in-memory sort was, and it turns out it's the size of all sorted documents combined.

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-3973 add wc example for bulk.execute()
DOCS-4065: Fix old legacy links in 2.0 and 2.2 release notes

Signed-off-by: Sam Kleinman <samk@10gen.com>
DOCS-3483: additional emphasis
DOCS-2145: note and organization about elections
DOCS-3924: clarification about acknowledged write concerns
DOCS-3373: Chunk migration builds indexes

Signed-off-by: Sam Kleinman <samk@10gen.com>