The baseconfig module (configuration variables) is now modularized in two
ways.


1) The definition of configuration variables has moved from the database to
dedicated .json files, which can be defined by one or multiple additional
modules. This means the database table "settings" is no longer in use.
As an example, see the module "baseconfig_bwlp".
If you only enable the module "baseconfig", you will find that visiting
the "configuration variables" menu entry in slx-admin shows a pretty empty
page. However, if you additionally enable the baseconfig_bwlp module, many
configuration variables will be shown.
baseconfig_bwlp doesn't contain any config.json or page.inc.php, as its
sole purpose is to supply wanted configuration variables. This is achieved
by supplying two .json files.

./modules/<module>/baseconfig/categories.json: Defines categories for
configuration variables. Syntax is <id>:<sort-order>

./modules/<module>/baseconfig/settings.json: Defines configuration variables
to be shown by the baseconfig page. This has taken the place of the settings
table from the database and contains pretty much the same information.

Note that you can have multiple modules that supply categories.json or
settings.json files. They will all be honored by the baseconfig module.

2) You can hook into the baseconfig API mechanism (previously known as
the "getconfig" API) which creates the plain text output intended for
the clients. This way you can create more sophisticated output logic, or
simply have a nicer guy for some values you want to generate.
To hook into the API, you need a hook:
./modules/<module>/baseconfig/getconfig.inc.php
This code will run directly in the context of the baseconfig API request,
so you write code straight away that should add any configuration variables
to the associative array called $configVars, e.g.
$configVars['SLX_FOO'] = 'bar';
These values can be static, or queried from anywhere in the database, etc.
For an example of this, see the module "baseconfig_partitions_cdn"
Which is basically a normal slx-admin module with a GUI for creating a
partitioning config that get stored in the database.
It also contains the .../baseconfig/getconfig.inc.php hook that adds
the partition configuration to the output of the baseconfig API.