code cleanup in sexpression parser. lisp atoms can now contain : and ., but not be . alone

git-svn-id: http://gapt.googlecode.com/svn/trunk/source@1473 85d21ef8-add0-11de-ae77-5bfb9c5a3f34
moved to the new scala-maven plugin and enabled incremental compilation. this requires two changes: 1) we now depend on maven 3 (as a consequence of the new scala plugin). 2) maven needs more memory to run. please add export MAVEN_OPTS='-Xmx512m -XX:MaxPermSize=128m' to your environment variables. i will also write an email on that.

git-svn-id: http://gapt.googlecode.com/svn/trunk/source@1474 85d21ef8-add0-11de-ae77-5bfb9c5a3f34