If there is a SOVERSION then the versioned library is a real file and
the unversioned one just a symlink; better to have the real file be the
target.

- add gb_Library_UDK_MAJORVER variable for SOVERSION
- remove version parameter of gb_Library_set_soversion_script;
  instead hardcode the SOVERSION since it must be included in the
  file name in gb_Library_FILENAMES anyway
- store the unversioned symlink in the ILIBTARGET variable
- via new gb_Library_get_workdir_target_versionlink function
- removed gb_Helper_install call that resulted in both versioned
  and unversioned libs in instdir

Change-Id: I2c6f1698f0e39fdb2c07964d43ed9485cbca0b30