Added ability to generate dropdown from Enum field

Alternatively, if statement could be: if(substr($column->dbType, 0, 4) === 'enum'), however expected implemented option to be more robust across other database formats.

Created after followup on this issue:  https://github.com/yiisoft/yii/issues/292#issuecomment-44780779
Fix #3196: Masked input widget revamped to use new plugin
Fix #3196: Masked input widget revamped to use new plugin

Edited Asset Bundle PHP doc header information.
Formatting changes to new enum field
improved gii input filter, fixes #3689
Merge pull request #3676 from enigmatix/master

Added ability to generate dropdown from Enum field
refactored gii enum dropdown generator

PR #3676
`yii\sphinx\Connection::escapeMatchValue()` fixed
Merge branch 'master' of github.com:yiisoft/yii2
Merge pull request #3685 from kartik-v/3196-masked-input-revamped

Fix #3196: Masked input widget revamped to use new plugin
adjusted apidoc for MaskedInput widget
refactored ActiveRecord::unlinkAll() to work will noSQL

issue #3520
update changelog

[ci skip]
fix wrong template for min validation error
Merge pull request #3696 from superbull/patch-1

fix wrong template for min validation error
Docs about mail debugging added
fixed breaking Gii preview when file is unchanged

fixes #3693
fixed test break
added CHANGELOG for #3693
added explicit comment about file transport to mail config

fixes #3694