Add CharterSchoolApproval elements

Add elements CharterApprovalAgencyType and CharterApprovalYear to the School Domain entity as follows:

CharterApprovalAgencyType
+will be of type CharterApprovalAgencyType enumeration type
+CharterApprovalAgencyType enumeration type will have the following enumeration values...
_____State board of education
_____Public charter school board
_____University
_____Other
+Annotation: The type of agency that approved the establishment or continuation of a charter school.
+CEDS source: https://ceds.ed.gov/CEDSElementDetails.aspx?TermId=8258

CharterApprovalYear
+will be of type SchoolYear
+Annotation: The school year in which a charter school was initially approved.
+CEDS source: https://ceds.ed.gov/CEDSElementDetails.aspx?TermId=8259