Makes the following changes to ensure v2 + v3 compatibility:

- Use the same signature as the v2 abstract plugin manager.
- In the constructor, call `addInitializer()` instead of adding initializers to
  the configuration array; guarantees compatibility.
- Add `$shareByDefault` property as alias for `$sharedByDefault`.

…mework#56

- Each of which have been merged to this patch.

- zend-filter 2.6
- zend-stdlib 2.7/3.0
- zend-math 2.6
- zend-config 2.6

- Updates all dependencies to stable versions; if the dependency has
  forwards-compat changes for v3 components, pins to those.
- Selectively skip zend-db, zend-session tests when testing against
  servicemanager v3.

ValidatorPluginManager:
- Removed all barcode adapters from aliases and factories; these are not actual
  validators, but consumed by the barcode validator.
- Used `$plugin` terminology over `$instance` for validation.
- Modified `validatePlugin()` to throw v2 exception.
- Added factory entries using normalized names to ensure BC with v2.
- Used `$container` verbiage over `$locator` verbiage.
- Updated `injectTranslator` to check if being used in a v2 context; if
  so, it pulls the translator from the parent container.
- Simplified tests for translator injection verification using Prophecy.
- Updated tests for expected exceptions to test for either v2 or v3 exceptions.
- Added compatibility tests.

StaticValidator:
- Configure the "share by default" flag based on version of
  zend-servicemanager.