- updated pointers to sbt
- better debug printout
- prints its own arguments
Just found out that ``git fetch`` only synchs the remote branches. If you want
to fetch the tags as well, you need an additional ``git fetch --tags``.
Added step for building the worksheet

I had to add three new variables in order to have the
flexibility of building the worksheet when running this
script:

* $ECLIPSE_PLATFORM is needed to select the right
profile to pass to the Worksheet build.
* $BUILD_PLUGINS allows to build the Scala IDE alone,
which is useful for instance when using this script in a
Jenkins job for producing a nightly.
* WORKSHEET_BRANCH is the branch in the Worksheet
GH repository to use when to building the Worksheet.

Re #1001426
Clean up all local changes before building a project

This is done to avoid the script fails because of  some
local change. For instance, when setting the bundles'
version in the MANIFEST via the "set-versions" profile,
some local change is created (in the specific case, a
copy of the MANIFEST, i.e., MANIFEST.original). If we
don't clean up, next time the script is run it will fail.
Updated README to reflect last changes in the uber-build script.
Cleaned up script formatting