Add more default anonymization values

Added series date, series time and Institutional department name to the
list of elements that are anonymized by default.
Revert "Add more default anonymization values"

This reverts commit bf7709f50cc5d64f225079e8f137666507c32109.
Added more default anonymization values

Series date, series time and institutional department name were added to
the list of default values.
Added Anonymizer#to_anonymizer
Added DObject#anonymize method

This is a convenience method for quickly anonymizing a single DICOM
object.