Enh #2131: Added Accept header parsing to CHttpRequest to give an array
of accepted types in order of preference
Merge remote-tracking branch 'upstream/master' into
2131-add-accept-header-parsing

Conflicts:
	CHANGELOG
Moved position of line to follow numerical order.
Added #135 back in changelog, which got lost somehow..
Separated out parse and compare functions.
Reduced regular expression count to 2 from 3.
Modified MIME type array map structure.
Merge remote-tracking branch 'upstream/master' into
2131-add-accept-header-parsing

Conflicts:
	CHANGELOG
Typo corrections
Altered parseAcceptHeader() to use only one regexp.
Thanks to Ka on StackExchange for this expression.
Merge branch 'master' of git://github.com/yiisoft/yii into 2131-add-accept-header-parsing

Upstream merge.
Typo corrections and code tidy up.
parseAcceptHeader() function description tidy up.
Added unit test file for CHttpRequest for the methods
parseAcceptHeader() and compareAcceptTypes().
Modified the regexp in parseAcceptHeader() to accept wildcards in the
path.
Modified the description of compareAcceptTypes() to better reflect the
comparison result (higher preference returns lower value, so that most
preferred is first in the array).
Merge branch 'master' of git://github.com/yiisoft/yii into 2131-add-accept-header-parsing

Merge from upstream.
Undo accidental permissions change on bootstrap.php
Transferred data for unit tests from the test functions into data
providers.
Removed unnecessary spaces.
Yii code style correction
Allow creation of new validators on the fly

This is useful for extensions and/or behaviors.
I could do it outside the model, but I think it belongs in it.
Update changelog
now return $this allowing method chaining

also added @since tag