Factor out the script text column into a new table: 'script'

Create new linking table 'pkg_script' to express the relation between
packages and scripts.

Drop old scripts table and repalce with view + triggers to emulate old
behaviour.
Add backwards compatibility view and triggers to local.sqlite schema.

Fix indentation in libpkg/private/db_upgrades.h
The table is 'pkg_script' not 'package_script'

Be consistent with curly brace position after if ()

Update SQL to account for new pkg_script and script tables.
Clean out any unreferencec scripts from the script table.

Tidy up some of the inline SQL
Create the pkg_script_package_id INDEX correctly

Factor out code as new pkg_install_scripts() function

Get the arguments to the SCRIPTS2 SQL prstmt in the correct order.