It used to be that you would give the target table name as an option to the
PostgreSQL connection string, which is untasteful:
load ... into pgsql://user@host/dbname?tablename=foo.bar ...
Or even, for backwards compatibility:
load ... into pgsql://user@host/dbname?foo.bar ...
The new syntax makes provision for a separate clause for the target table
name, possibly schema-qualified:
load ... into pgsql://user@host/dbname target table foo.bar ...
Which is much better, in particular when used together with the target
columns clause.
Implementing this seemingly quite small feature had impact on many parsing
related features of pgloader, such as the regression testing facility. So
much so that some extra refactoring got into its way here, around the
lisp-code-for-loading-from-<source> functions and their usage in
`load-data'.
While at it, this patch simplifies a lot the `load-data' function by making
a good use of &allow-other-keys and :allow-other-keys t.
Finally, this patch splits main.lisp into main.lisp and api.lisp, with the
latter intended to contain functions for Common Lisp programs wanting to use
pgloader as a library. The API itself is still the same as before this
patch, tho. Just in another file for clarity.
