Add rudimentary Webmin module config option

[rdmark]

While I think installing Webmin proper is beyond the scope of our autoconf macros, if Webmin is already installed, it would be nice to have the option to add the netatalk(2|3) module and configure it with the correct conf file paths.

One idea:

• Add a --with-webmin-module autoconf option
• It checks for the existence of webmin (e.g. /usr/share/webmin on Debian or /usr/libexec/webmin on Fedora)
• If found it fetches the latest version of the netatalk(2|3) webmin module tarball and runs the install script, e.g. @${WEBMIN_DIR}/install-module.pl netatalk3*-wbm.tgz
• It modifies the netatalk webmin module's config file to have it point to the correct file system paths for all config files

Ex. for netatalk2:

		echo "applevolumedefault_c=$(sysconfdir)/netatalk/AppleVolumes.default" >> config; \
		echo "applevolumesystem_c=$(sysconfdir)/netatalk/AppleVolumes.system" >> config; \
		echo "afpd_c=$(sysconfdir)/netatalk/afpd.conf" >> config; \
		echo "atalk_c=$(sysconfdir)/netatalk/atalk.conf" >> config; \
		echo "papd_c=$(sysconfdir)/netatalk/papd.conf" >> config; \
		echo "afpd_d=$(sbindir)/afpd" >> config; \
		echo "atalkd_d=$(sbindir)/atalkd" >> config; \
		echo "papd_d=$(sbindir)/papd" >> config; \
		echo "netatalk_c=@PAMDIR@/etc/pam.d" >> config; \

[ghost]

What is Webmin?

[rdmark]

It's a webapp framework for system administration. We have a webmin module for netatalk: https://github.com/Netatalk/netatalk-webmin