Small improvement for transforming sums of products
Fixed some tests which failed because of syntax changes.

(7 + x) /= (x + 7)...
Simplify's now able to better factor out in fractions

Before:
simplify $ ((y * x * y) / (x * y * y)) --> x * (y)^(2.0) * (x * (y)^(2.0))^(-1.0)
Now:
simplify  $ ((y * x * y) / (x * y * y)) --> 1.0
Some more little changes without huge effect.
Removed superfluous multiplication with 1
enhanced simplifySum's factor-out entry point
Add parsers for Abs and Signum
New exp rule: euler^(ln(x) * y) = x^y

And some tests testing this as well as (x^y)^z = x^(y*z)
Infrastructure for pulling common exponents out of a product
Re-structured chaos at the bottom of Symmath.Simplify (a bit)

It's still a mess...
Restored canceling abilities

re: existential crisis
Six more tests will improve test coverage a lot.
Better function table, width aligned fields

(thanks to Text.Printf)
Improved product transformation etc
Improved function table functions radically

At this point, a rather good-looking function table can be printed with
this call and looks like the below shown table:

ghci> defaultFunctionTable 0 40 10 (Fraction 1 (Variable 'x'))
              x       (1.0 / x)
--------------- ---------------
         0.0000        Infinity
        10.0000          0.1000
        20.0000          0.0500
        30.0000          0.0333
        40.0000          0.0250

We're also not using any third-party packages anymore for
pretty-printing but the standard Text.PrettyPrint.
Could remove three other rules from simplifyProd
Symmath, Release III.

Merge branches 'pu/simplify', 'pu/parse' and 'pu/funtable' into next
Merge branch 'next'