Distinguish rake assets:clobber from rake assets:clean
Fix confusing exception in ActiveSupport delegation
Have Postgres OID types inherit from general types

Using general types where possible. Several more can go away once
infinity gets figured out.
Replace `type_cast` case statement with delegation

All subclasses of column were now delegating `type_cast` to their
injected type object. We can remove the overriding methods, and
generalize it on the `Column` class itself. This also enabled us to
remove several column classes completely, as they no longer had any
meaningful behavior of their own.
fix multiple hash preloads.  Fixes #14994
Merge pull request #15201 from sgrif/sg-types-postgresql

Have Postgres OID types inherit from general types
make the each visitor top-down left-right
prepopulate the dispatch cache so we don't need the ThreadSafe cache.
Merge pull request #15187 from v-yarotsky/fix_confusing_delegation_exception

Fix confusing exception in ActiveSupport delegation
Merge pull request #15203 from sgrif/sg-delegate-type-cast

Replace `type_cast` case statement with delegation
Merge pull request #15191 from camsong/master

Distinguish rake assets:clobber from rake assets:clean

[ci skip]
Use the generic type map object for mysql field lookups