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.
Working on pkg-metadata man page
Work in progress
Recover after misadventures  with 'git stash'
Add installation timestamp as local metadata that won't be included in
a pkg tarball.
Add 'mtree' to the list of metadata.  Sort list by name.