Email components hierarchy created.
SwiftMailer applied as email solution.
Unit tests for \yii\email\swift have been improved.
Methods 'addText' and 'addHtml' added to \yii\email\BaseMessage.
'\yii\email\ViewResolver' added.
Email message render functionality added.
Email message interface extracted.
Merge branch 'master' of github.com:yiisoft/yii2 into email-swift-2
'email' renamed to 'mail'.
'SwiftMailer' recomposed into extension.
Vendor testing support provided.
'swiftmailer' extension unit tests fixed.
'MessageInterface::createAttachment()' renamed to 'MessageInterface::attachContentAsFile()'
Method 'MessageInterface::__toString()' added
BaseMailer::defaultMessageConfig published as BaseMailer::messageConfig
Merge branch 'master' of github.com:yiisoft/yii2 into email-swift-2
Merge branch 'master' of github.com:yiisoft/yii2 into email-swift-2
Interface 'MailerInterface' extracted.
Method 'MailerInterface::createMessage()' added.
'yii\mail\ViewResolve' removed.
Interface 'ViewContextInterface' applied to BaseMailer.
'yii\mail\MessageInterface' file related methods interface adjusted to use options, embed file methods added.
'yii\mail\MessageInterface' methods 'addText()' and 'addHtml()' removed.
Email message charset setup added.
Merge branch 'master' of github.com:yiisoft/yii2 into email-swift-2
Proposal for accessing populated relations

fixes #842

- allows checking whether a relation has been populated
- getting a list of relation names that have been populated
- getting all populated relation data

todo:

- [] add phpdoc
MessageInterface::render() replaced by MessageInterface::renderHtml() and MessageInterface::renderText()