Upgrade Bootstrap from 3.1 to 3.2

Fix json format in gii/generators/extension/default

* upstream/master:
  resolved naming conflict in apidoc

* upstream/master:
  gridview and listview use widget ID in base tag
  typo fix [skip ci]
  Update CHANGELOG.md
  made elasticsearch error messages more readable
  Spanish structure-views [skip ci]
  Fix filename
  Update README.md
  https://github.com/yiisoft/yii2/pull/4091#discussion_r14296860
  Fix possibility of non-removed symlinked directory.
  Fixed typo. [skip ci]
  changed default for rotateByCopy of FileTarget

Spanish structure-views [skip ci]

Fix filename

PS: should `start-looking-head.md` be `start-looking-ahead.md`? I remembered that is called look ahead.

Fix possibility of non-removed symlinked directory.

works on windows out of the box now.
fixes #3989

fixes issue #3989

Fixes #4080, FileHelper::removeDirectory() symlinks handling enhancements