Added Factory, see #25

[hiqsol]

Q	A
Is bugfix?	no
New feature?	yes
Breaks BC?	no
Tests pass?	yes
Related issues	#25, #26

Actually changes are minimal but are shown huge because of renamed file. Done in three commits to allow explore diffs.

Highlights:

• AbstractContainer
  • protected build($id, $config)
  • protected buildFromDefinition($definition)
  • Factory
    • public create($id, $config) - new instance every time
  • Container implements PSR11
    • private $instances
    • public get($id) - same instance every time

[samdark]

Looks good to me but need docs and readme adjustments.

[SilverFire]

Yii::$di->get() and Yii::createObject() methods with old container implementation work as factory. This pull request does not restore the original behavior, but make is theoretically possible. How are we going to keep a sort of behavioral BC with the existing user-side code?

[hiqsol]

Please refine what behavior can not be reproduced?