Add possibility to json decode to array

This pull request improves the decode method of the
Concrete5_Helper_Json class to allow decoding objects to php arrays
instead of stdClasses
unused Loader::db removed
sanitize user added select attr values

http://www.concrete5.org/index.php?cID=471278&editmode=
Remove Unused `Loader::db()` Call

Remove unused `Loader::db()` call from
`PageOwnerPermissionAccessEntity::load()`
Fix EnvironmentRecord caching for core segments without package handle
Fix Error Set in Page Type Dashboard Page

Fix error set in page type dashboard page

Current method user `$this->set()`

- Change to `$this->error->add()`
Merge pull request #1041 from mkly/fix_page_type_dashboard_error_message

Fix Error Set in Page Type Dashboard Page
Merge pull request #1019 from mkly/remove_unused_db_call

Remove Unused `Loader::db()` Call
Merge pull request #983 from Remo/patch-39

unused Loader::db removed
Merge pull request #935 from mlocati/json-decode-to-array

Add possibility to json decode to array
Merge pull request #1005 from Remo/patch-40

sanitize user added select attr values
Merge pull request #1039 from zemm/fix/environment-core-caching

Fix EnvironmentRecord caching for core segments without package handle