improved fixture controller

guides fixed/improved

Info about retaining the default scenario

to allow specific styling
also fixed an issue with gridview sort indicator css.

fixes #1000

fixes #1744

fixes #1787

the LogPanel already filters out profile so it does not make sense
adding it here.

[ci skip]

Fixtures controller docs

this will result in objects that do not have the property anymore :-)

as requested in
https://github.com/yiisoft/yii2/pull/1781#issuecomment-31587963
https://github.com/yiisoft/yii2/issues/1478#issuecomment-31576474
fixes #1478

timings fixed

Update migration.md

dots do not work.

FixtureController code style fixes and typo fixes