Corrected documentation regarding validation errors

Added some more documentation for define_readers and define_writer of the Association and its inherited classes

Cleaned up rdoc a bit emphasizing that callbacks are called. Also
removed the stress on the fact that records are always removed.

If callbacks return false then records will not be deleted.

Conflicts:
	activesupport/lib/active_support/callbacks.rb

Replace multi_json with json

Adding documentation to the automatic inverse_of finder.

Avoid method missing when calling assume_migrated_upto_version (master)

Call assume_migrated_upto_version on connection to prevent it from first
being picked up in method_missing. In the base class, Migration,
method_missing expects the argument to be a table name, and calls
proper_table_name on the arguments before sending to connection. If
table_name_prefix or table_name_suffix is used, the schema version changes
to prefix_version_suffix, breaking `rake test:prepare`.

Fixes #10411.

read_attribute_before_type_cast should accept symbol

Don't modify args in TableDefinition#primary_key

Clean up unused method for `rake doc`.

This is the compination of #10057 and 10534.

Closes #10320

Escape of U+2028 and U+2029 in the JSON Encoder

Conflicts:
	activesupport/lib/active_support/json/encoding.rb

Since Ruby 2.0 is UTF-8 by default we need to explictly say that the
encoding of this file is US-ASCII

Escape multibyte line terminators in JSON encoding

Cleanup finder methods