fixes #877

'yii\mail\MessageInterface' file related methods interface adjusted to use options, embed file methods added.

Interface 'ViewContextInterface' applied to BaseMailer.

Method 'MailerInterface::createMessage()' added.

Proposal: creating ViewContext interface to determine view name

typo fix

s/value to be cached value/value to be cached/g

code style

Control statements based on the if and elseif constructs must have a single space before the opening parenthesis of the conditional and a single space after the closing parenthesis.

as requested in issue #1084

Messageformatter refactoring

pgsql: added 'bool' type (alias of 'boolean')

Relates #1086 and #1087

Messageformatter refactoring

* master:
  ensure parameter types in baselistview message
  added unit test to verify AR afterSave isNewRecord value

fixes #1072

closes #1084

Update FallbackMessageFormatter.php

Fix declarations for yii\i18n\FallbackMessageFormatter::format() and yii\i18n\FallbackMessageFormatter::formatMessage()