Prepare maven-based distribution building.

NOTE: `maven/latest/build.xml` is now deprecated.

To publish a Scala build, simply call `ant publish` or `ant publish-local`.
`maven/latest/build.xml` will soon disappear from `dists/`

The idea is that a Scala distribution is a simple
repackaging of artifacts already available on maven.

Already available: typical jars for the artifacts (classes, sources, scaladoc).
To add: the bin/, doc/, and man/ directories.

Thus, move the contents that should end up in the distribution
from docs/ to doc/, create the man/ directory with the manpages,
and include the scripts in bin/.

Next up: package these directories in a jar and publish to maven,
with a dependency on scala-library-all, scala-reflect and scala-compiler,
for the jars that should end up in the distribution.

Refactorings:
 - Pull filter-pom out from deploy-one.
 - Rename maven-base to dist.maven.
 - Set all properties in the init target (dist.maven)
scala-dist: all you need to roll your own scala distribution

We now publish a scala-dist artifact every time we publish to maven.
It captures everything needed to build a Scala distribution.

The packager should resolve all transitive dependencies of scala-dist,
put the class-file jars in the lib/ directory,
the scaladoc jars in the api/ directory,
and the source jars in the src/ directory,
in addition to unpacking the scala-dist jar itself,
which contains the bin/, doc/ and man/ directories,
which previously weren't available on maven.

This also removes the `@{dir}` abstraction, which was used to
package the continuations plugin. Since it's moved out,
we can go back to hard-coding it.
scala-library-all: dependency for those who want it all

If you'd rather depend on all Scala has to offer, module-wise,
depend on scala-library-all. This dependency determines the
jars that ship with the Scala distribution. To achieve parity
via maven resolution, this is the artifact to depend on.