This is mostly to avoid further error when users don't defined a database table prefix. it's recommenced to define one anyway.
Also enable verbose migration so we'll be able to actually view SQL queries (and execution time).
* Move `Makefile` to `GNUmakefile`, which GNU `make` picks first
* Add `Makefile` so other `make`s forward to `gmake`
* Set the `SHELL` variable and let `make` handle the shell
Signed-off-by: Olivier Mehani <shtrom@ssji.net>