Configuration, Dependency Injection services, and some usabilities tweaks

A significant overhaul of the pager bundle to facilitate using the pager via DI, as well as some usability improvements. All changes and new features should be BC compatible.

#### Adapter/PagerAdapterInterface:
 * Added a `countResults()` method to the interface which returns the the number of results for an optionally provided offset and limit. This method now powers the `getTotalResults()` methods in both concrete implementations

#### Adapter/DoctrineOrmAdapter:
 * Removed the redundant default value of null ( '= null') from the totalItems property.
 * Renamed the `$query` property to `$queryBuilder` for clarity.
 * Made the $queryBuilder (formerly query) constructor argument optional and added new `set/getQueryBuilder()` methods (DI Improvements)
 * Made the adapter implement `\Countable` via `count()` method which returns totalResults
 * Added optional offset and limit parameters to `getCountQuery()`
 * Implemented `countResults()` to call `getCountQuery()` and cache results per `$offset` and `$limit` arguments.
 * Changed `getTotalResults() to use the new `countResults()` method
 * Added `get/setHydrationMode()` (DI Improvements)

#### Adapter/ArrayAdapter
 * Removed the redundant default value of null ( '= null') from the totalItems property.
 * Made the array constructor argument optional and added new `set/getArray()` methods (DI Improvements)
 * Implemented `countResults()`
 * Changed `getTotalResults()` to use the new `countResults()` method

#### Pager:
 * Implemented `\Countable` and `\IteratorAggregate` to provide simpler pager usage:
    * `count($pager)` / `{% results|length %}` - Returns the number of results in the current page
    * `foreach($pager as $result)` / `{% for result in results %}` -- Iterates through the items in the current page of the pager
 * Made the `$adapter` constructor argument optional and added new `set/getAdapter()` methods (DI Improvements)
 * Fixed whitespacing around `$maxPages` property
 * Added `getPageCount()` method. I would recommend a check on this method be the preferred way to check if results should show the paginator (`isPaginable()` is an unusual name and not immediately clear what it's checking):
    `{% if results.getPageCount() > 1  %}  {{ paginate(result, …) }} {% endif %}`
 * Moved min-page handling from `setPage($page)` to `getPage()` and removed the call to `setPage(...)` inside `setLimit(…)` to allow for DI usage (setting the limit on instantiation was causing a call to `setPage()` and the `getLastPage()` call within was triggering an error when the adapter didn't yet have a queryBuilder).
 * Changed all calls to `$this->page` to `$this->getPage()` to support the later-in-life min-page handling mentioned above.

#### Resources/config/adapters.xml
 * Added DI definitions for both adapters: `maker_labs_pager.adapter.doctrine_orm`, `makers_labs_pager.adapter.array`

#### Resources/config/services.xml
 * Added DI definition for `maker_labs_pager.pager` with a null adapter parameter and defaults for limit and max_pages as provided by new configuration options (see below)
 * Reconfigured service definition for `makerlabs.twig.extension.pager` (see below)
 * Added template config  parameter as argument to `makerlabs.templating.helper.pager` definition.
 * Changed tempting argument for `makerlabs.templating.helper.pager` to be the default templating engine, instead of the php-only engine.
 * ***NOTE:*** All new service terms use the more-properly normalized 'maker_labs_pager' rather than the previous 'makerlabs_pager' prefix (which was left in-place wherever it was already used). This better matches the Symfony style of bundle name inflection.

#### DependencyInjection/Configuration
 * Added configuration options under the maker_labs_pager root node: limit, max_pages, and template (DI Improvements). All options are optional with defaults that match the previously class-hardcoded defaults.

#### DependencyInjection/MakerLabsPagerExtension
 * Added configuration handling
 * Dynamically clones the `maker_labs_pager.pager` service into 2 adapter-specific services (with the same configuration directives as the generic service): `maker_labs_pager.doctrine_orm_pager` and `maker_labs_pager.array_pager`.

#### Twig/Extension/PagerExtension
 * Now proxying calls to `Templating/Helper/PagerHelper` to reduce code duplication.
 * Passes through the default template as defined in configuration, or if omitted, `MakerLabsPagerBundle:Pager:pagination.html.twig`

#### Templating/Helper/PagerHelper
 * Accepts a default template from configuration, or a call-time template (which might be the PagerExtension twig template), or if neither, uses `MakerLabsPagerBundle:Pager:pagination.html.php`.