added kernel.cache_clearer tag to the ref
Update database.rst

Changed to the correct value on assertEquals()
Merge pull request #2608 from pvolok/cache_clearer_tag

Added kernel.cache_clearer tag to the reference
Merge pull request #2610 from biruwon/2.1

Update database.rst
Corrects exception controller name
Update introduction.rst

Changed $_FILE to $_FILES
Merge pull request #2612 from langj/fix-controller-name

Corrects exception controller name
Merge branch '2.0' into 2.1
Merge branch '2.1' into 2.2
[#2612] Updating exception controller for 2.2 change