Modify components to make them compatible with `slapos.recipe.cmmi` shared mode.

Most of them were straightforward, except:

 - aspell, where all dictionnaries parts were installed in aspell part. Instead of this, we generate an aspell wrapper for each language. This wrapper runs aspell with environment variables so that it loads dictionnaries from the language.
 - fonts, where all fonts were installed in the same `${buildout:parts-directory}/fonts/` folder and where just installing a font part had the side effect to make this font available to every application. Now each font is installed separately and it becomes applications responsability to generate a fontconfig's fonts.conf and set `FONTCONFIG_FILE` environment variable to load it, as described in https://www.freedesktop.org/software/fontconfig/fontconfig-user.html . A new `template-fonts-conf` section was introduced for this.
 - mariadb, where mroonga plugin write in mariadb's folder. For this, mroonga plugin is installed in another directory along with all original mariadb's plugin (that are copied) and mariadb service is configured to use mroonga's plugin folder instead of the default mariadb's folder.

See merge request !706