Cleaning for collections. Persistant database collection.

- Added `destroy` method and event to Collection and QueryCollection
which will unbind all listeners on itself and children
- `createCollection` now renamed to `extendCollection` as we now create
collections and blocks within the constructor, and just extend them on
each load, extending now support destroying old collections - this
allows us to persist the same database collection
Merged master into dev-cleancollections
v6.25.0. Improvement.

- v6.25.0 March 10, 2013
	- Database is now persistant
	- We now destroy unused collections
v6.26.0. Bugfix.

- v6.26.0 March 12, 2013
	- Node v0.10.0 support - fixes the "Arguments to path.join must be
strings" errors
	- The requirement of "plugins must have their own `package.json` file
with `version` and `main` defined within them" is now enforced
	- Updated dependencies
		- [backbone](http://backbonejs.org/) 0.9.9 to 0.9.10
		- [iconv](https://github.com/bnoordhuis/node-iconv) ~2.0.2 to ~2.0.3
		- [request](https://github.com/mikeal/request) ~2.12.0 to ~2.14.0
Added attribution for node 0.10 fix in changelog
v6.26.1. Improvement.

- v6.26.1 March 12, 2013
	- We now gather statistics on the node version and platform you are
using to better understand where issues are coming from
	- Updated dev dependencies
		- [coffee-script](http://jashkenas.github.com/coffee-script/) ~1.4.0
to ~1.6.1
		- [request](https://github.com/mikeal/request) ~2.14.0 to ~2.16.2
v6.26.2. Bugfix. Improvement.

- v6.26.2 March 23, 2013
	- Fixes `TypeError: Object #<Object> has no method 'removeListener'`
		- Thanks to [Steven Lindberg](https://github.com/slindberg) for
[issue #462](https://github.com/bevry/docpad/issues/462)
	- Can now customise the `watchOptions` that are used to construct the
[watchr](https://github.com/bevry/watchr) instances we create
	- Updated dependencies
v6.27.0. Improvement.

- v6.27.0 March 25, 2013
	- Engine requirements are now:
		- node >=0.8
		- npm >=1.2
	- Iconv is now a lazy loaded dependency
		- Thanks to [jhuntdog](https://github.com/jhuntdog) for [issue
#468](https://github.com/bevry/docpad/issues/468)
	- Added `regenerateDelay` configuration option
		- Thanks to [Homme Zwaagstra](https://github.com/homme) for [pull
request #426](https://github.com/bevry/docpad/pull/426)
v6.28.0. Improvement.

- v6.28.0 March 25, 2013
	- Removed native prototype extensions
		- Thanks to [David Baird](https://github.com/dhbaird) for [issue
#441](https://github.com/bevry/docpad/issues/441)
		- If you were using `toShortDateString`, then we'd recommend [this
gist](https://gist.github.com/4166882) instead
		- If you were using `toISODateString`, just replace it with
`toISOString`