Merge dist.xml and braille.xml
Misc changes:

- remove ${dollar} escaping because it wasn't needed and was not used consistently
- put dev-launcher in a separate profile that disables the main distribution
  (because there's no need to build them both at the same time)
- include the braille modules with `-P incl-braille` instead of `-DincludeBrailleModules`
- edit README
Add `debian` profile for building a Debian package

* Using the unix-maven-plugin. This plugin can also be used to create
  packages for other Linux distributions.
* The config and log directories were made configurable because on Linux
  these are typically stored under special locations (/etc and /var/log).
* A distinction was made between configuration files that we want to
  expose to the user (system.properties and config-logback.xml), and
  internal configuration files.
* The modules are treated as variable data (stored under /var) with the
  upcoming installer/updater feature in mind.
* A special version of bin/pipeline2 had to be made in order to set the
  correct locations of the data directory and system.properties.
* Added a daemon script for starting and stopping the pipeline server.
* The debian profile disables dist-assembly and dev-launcher-assembly
  because the properties defined in the profile would overwrite
  dev.properties and dist.properties. Also, the .deb is not attached as
  an artifact, so it doesn't make sense to build the assemblies at the
  same time.
* Updated README
daemon script: add PATH so that start-stop-daemon can be found
Added prerm, preinst, postrm and postinst scripts

They do the following:

* prompt for admin userid and password during first installation
* merge old and new configuration files during upgrades
* start the daemon after installing or upgrading
* stop the daemon before removing or upgrading
* ...
Make braille profile independent of unix-maven-plugin
Change project "type" to pom

because we there's no need to create a JAR
small POM fix
fixes in postrm script
Build debian package with jdeb instead of unix-maven-plugin
Add config file for daemon