Garbage prevention.

* Remove debug echo
* Instead of accepting possible garbage, sanitize by using available "multiple fields" properties to determine whether or not data should be an array.

Fix for 0.8

Version 0.7 only used get_metadata_field_value() to to call private method, and always expected an array. This change improves compatibility with 0.8+, where a string could occur.

Shuffling of code to avoid checking if_array() twice
Merge branch 'master' of github.com:connerbw/custom-metadata