Incosistent access modifiers in JDBCUserStoreManager

[danijelt]

Description:
JDBCUserStoreManager has incosistent access modifiers in addProperty, addProperties, updateProperty and updateProperties. addProperty is public, updateProperty is protected and add/updateProperties are private.

When writing custom user store manager that inherits JDBCUserStoreManager, if we want to override these 4 methods, we need to fully reimplement them, as well as persistUser, doSetUserClaimValue and doSetUserClaimValues.

Affected Product Version:
WSO2 IS 5.9.0

Steps to reproduce:
Write custom user store that extends JDBCUserStore, try to override addProperty, addProperties, updateProperty and updateProperties. Only addProperty and updateProperty can be overridden.