ZF-8297: Rework Zend_Validate_NotEmpty

Description

The NotEmpty validator should be reworked so that it is possible to define which values should be detected as being empty.

For example: Someone could be in need of string '' to be not detected but null being detected as empty.

All values which are detected as being empty should be configurable so they could be switched on and off for validation.

Comments

Rework finished within Incubator (r19498) and waiting for acceptance to core.

New implementation accepted and cored with r20020