Currently only implement --backup to get list of (config) files in
protected directories to backup.

This also fixes a database corruption bug in database.c.

In quiet mode e.g. "apk info -q -W <file list>" a list of dependencies
suitable for .PKGINFO is output in one line.

Was broken by earlier ROOT environment commit.

dependencies are separated with single space rather than ', '.
makes db file slightly easier to parse from a shell script which
might be handy.

so far it only lists installed packages

This reverts commit b852d670.

Each dep is separated with a single space. I.E:

D:dep1 dep2 dep3

Defaults to /etc/apk/repositories, absolute path and not relative
the install root.

Make the db of installed packages more similar to index file and
reuse the code. Also rename the database file.