Database install/update (migration) scripts

[Matt Giuca]

Provide a script (ivle-installdb) to install the database, and another one
to run all the necessary migrations (ivle-updatedb).

The database should store a table with every migration that's been applied.
The update script should automatically install any migrations which haven't
been applied, in order.

Note: Need to take into account how the debian package will use these.

[Matt Giuca (mgiuca)]

Update RE Debian package: The Debian package system (apparently) has a way of doing
database migrations which would supersede our own script (but only for debian packages).

This means this script is only required for non-Debian-package based installation.
Hence it is desirable, but not critical.

(A brief summary of the Debian way to do it, as I gather from Will's description: You
have a directory for each debian version, and this directory contains all of the
migrations between the last version and this. The installer automatically runs the
scripts in all the directories between the previously-installed version and the new
version. This is quite different from our non-Debian method, which would involve
keeping track of all the installed migrations.)