Merge pull request #34 from michalt/semilinear

Tests
new version of recursive-star (more efficient)
two new testgrammars... results seem very wrong!
fixed a serious bug in make_free function.
This affected the whole Newton-iteration if coefficients of monomials were 1.
non-commutative polynomials should be usable now
comments + small change in monomial (yesterday's meeting)
-Fixed (rather dirty..) the symbolic-delta computation.
-Added new test-grammar (bintrees_float.g, least solution there is 2/3)
-float-sr computes with doubles now
newton: some cleanup
monomial: fix type