Improved version handling; clean-up.

Removed old smtlib2/smtlib Main files, which are superseeded by
smtinterpol/Main.  Removed old version handling (Version.java).
The version is now read from a property file.  This property file
is created by the ant build script.  If the property file is not
present (e.g. in a local git checkout) unknown-version is given
as version string.  The version string now also contains the
information whether it is the competition version.