2021/11/08/data objects refactoring

I'm making some changes to the data objects management system for #Ferreteria v0.5.

at present

Database instantiation is currently done by cDatabase::Instantiate(), which uses an internal static table to look up the cDatabase-descendant to instantiate from a slug returned by cDatabaseSpec->GetTypeString().

I suddenly realized that this makes no sense:

• the cDatabaseSpec-descendant should just return the class it wants to use, from ->GetDatabaseClass()
• cDatabaseSpec can instantiate directly, e.g. cMainDBSpec->MakeDatabase().
• cDatabase should be named caDatabase, because it is abstract.

TO DO

• rename cDatabase to caDatabase
• rename cDatabaseSpec to caDatabaseSpec
• replace abstract caDataSpec->GetTypeString() method with caDatabaseSpec->GetDatabaseClass()
• write caDatabaseSpec->MakeDatabase()