Allow key/value contenttype references in select fields.

Specify contenttype/key,name instead of just contenttype/value.

Bolt uses the first item internally, while the name is displayed in the
drop-down field.
Added contenttype-based select field to kitchensinks
PHP sux: Empty argument never be overriden with "" default parameter, so 'new Cache()' won't initializes with correct BOLT_CACHE_DIR
Merge pull request #1099 from rixbeck/master-org

PHP sux: Empty argument never be overriden with "" default parameter, so...