Fix RST title syntax
Revise "Migrating Schemas" documentation
Reintroduce HasLifecycleCallbacks annotation
AnnotationDriver should ignore inherited methods

Only consider methods declared in the current class being processed. This is consistent with ORM's AnnotationDriver.

See: https://github.com/doctrine/doctrine2/commit/67ae22b9118cd5bbd8a897b76ac68ffca263c4e2
Document reintroduced HasLifecycleCallbacks documentation

This documentation was originally removed in abcf27564c3ed18f6fa6b8084d75e393cb30ca5c, after the annotation itself was removed in e9af24994055f94aede98593e7c2c421ee6a0a22.
Improve AlsoLoad annotation documentation

Discuss how AlsoLoad may be used for methods, and link to migrations page.
Handle AlsoLoad methods like properties and without HasLifecycleCallbacks

AlsoLoad method annotations will no longer require the HasLifecycleCallbacks class annotation. The latter will just be used for lifecycle callbacks.

To be consistent with property handling, an AlsoLoad method may be registered with multiple fields. Fields will be considered in order and the method will be invoked at most once with the first value found.

Wrote additional functional tests for AlsoLoad behavior for both properties and methods.
Inherit AlsoLoad methods from parent's ClassMetadata
wip
Optimize checks for lifecycle callbacks and listeners
Do not allow duplicate lifecycle callbacks to be registered

Using the method name as a key in lifecycleCallbacks will ensure that methods are never registered (and invoked) multiple times. We'll still use the method name as the value so existing code can iterate over values in a lifecycleCallbacks event array to get method names.

Fixes #427, #474, and #695. Related to doctrine/doctrine2#903.
ClassMetadata should only invoke lifecycle callbacks on its own objects

Since each mapped document class has its own ClassMetadata, we can expect the exact class and reject inheriting classes.
Changelog entry for HasLifecycleCallbacks and AlsoLoad
Merge pull request #428 from doctrine/fix/gh427

Reintroduce HasLifecycleCallbacks annotation.