- 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
Now builds the Typesafe IDE

The uber-build script can now also build the Typesafe IDE, which is
based on the built Scala IDE + Worksheet.

Also updated the README.
Code formatting: replaced tabs with four (4) spaces
Pass the needed environment variables to the script as script's arguments.

This makes it much easier to print the set of variables that have been passed to the script.

Thanks @huitseeker for the great tip!
Integrated feedback comments from PR #5
Merge pull request #5 from dotta/issue/build-worksheet-and-typesafe-product-1001426

Issue/build worksheet and typesafe product 1001426