added minisat to readme

git-svn-id: http://gapt.googlecode.com/svn/trunk/source@1568 85d21ef8-add0-11de-ae77-5bfb9c5a3f34
* Fixed the stack overflow error during cut introduction in Grammar.scala (cutIntro still causes the stack to overflow, but in a different place).
* Put the definition of LK into user_manual.tex

git-svn-id: http://gapt.googlecode.com/svn/trunk/source@1570 85d21ef8-add0-11de-ae77-5bfb9c5a3f34