allow unit tests to requireApp() on setUp()
mod: don't create app in bootstrap script, unit tests do it themselves
add: option to destroy app after each test to find unit tests that fail
     to require an app
add: new key for unit tests config named "className". Allows to run the tests
     using different Application instances (consoleApp/ webApp)
mod: TestCase::getParam accepts second param $default=null
mod: incorporate suggestions
- rename requireApp() to mockApplication()
- always destroy app on tearDown()
  - eliminates need for constant YII_DESTROY_APP_ON_TEARDOWN
  - mockApplication() becomes a lot easier. Destroying app on each tearDown
    means creating it on every call is fine. No more checking if it already
    exists and if it has been created from the same config.
- \yii::$app should have been \Yii::$app
set application timezone early in application constructor, set default of UTC if no timezone is configured at all (not in app config nor in php.ini)
Merge commit '1ccce' into fix-209-default-timezone
undo commit 1ccce67f345ca33441fe22602e11cc62a31db371
Initial Gettext support.
Add exception classes hierarchy UML diagram.
better have timezone fix in application

app is resposible for setting time zone, so it should also do the
fixing.
+ documentation about the behavior.
issue #210 and #209
mod: don't use ArrayHelper to avoid loading another class during every request
remove fix for unset timezone from bootstrap app
fix: remove pointless unset
Fixes issue #50: implemented pager widgets.
Merge branch 'master' of https://github.com/yiisoft/yii2
Merge pull request #221 from resurtm/get-text-i18n

[WIP] Gettext support
Merge pull request #223 from cebe/timezone-fix

better have timezone fix in application
Merge pull request #210 from bwoester/fix-209-default-timezone

Fix issue #209 default timezone
Fixed duplicated merge.
RBAC: DbManager code style fixes