Remove error setting when reading/deleting non-existent key.
Fixes #3813
Merge pull request #1265 from ADmad/master-cakesession-valid

Ensure session is not invalidated after reading/deleting non-existent key.
Fixed curly brackets at a few class definitions
Merge pull request #1267 from djbobke/coding-style-fixes

Small coding-style fixes
Make note of method removal.