Make approach towards identifier quoting consistent

• Make the use of `` a general approach for explicit quoting of identifiers
• introduce AbstractPlatform::getRegularSQLIdentifierCase($identifier)
• Introduce AbstractPlatform::isRegularIdentifier($identifier)
• Fix Schema Assets not to lower-case, but to check for explicit quoting before.
• Filter values of identifiers passed to all platform functions when they are used in information schema queries according to `` explicit quoting rules.

Problem: Schema is independent of a vendor, this means we have to pick a behavior, i propose SQL-92

• http://savage.net.au/SQL/sql-92.bnf See <actual identifier>
• http://www.alberton.info/dbms_identifiers_and_case_sensitivity.html

This means:

• strtoupper() ALL tables, column, index, foreign key names that are not quoted by ``
• For any Quoted identifiers by `` the case is kept.
• We can introduce a validator to detect a schema that cannot be implemented with a given vendor platform.

In conjunction with the SQL reserved keywords tickets we can then improve the DatabaseDriver considerably to detect identifier casings