Fixes #1472: set event sender if possible.
make null format look nice by default
code style and docs
improved redis error message
Escape special chars in URL rules.
Moved extensions docs draft from wiki to main repository
Copied and adjusted 1.1 git workflow document
Added rules about namespace and package naming to extension docs
Added notes about github and screenshots to extension docs
Added $formName to Model::load().
Removed compatibility code for PHP < 5.4
Merge pull request #1479 from DaSourcerer/session-cleanup

Removed compatibility code for PHP < 5.4 in yii\web\Session
invalidate opcache of extensions.php file in composer installer

fixes #1480
doc typos
removed unused property from Session

cleanup after #1479
added CHANGELOGs for all the extensions

also filled framework CHANGELOG with relevant changes since alpha
fixed link in CHANGELOG
doc fix.
created proper progress bar

fixes #1293
fixed output in Console::select()