[Ant-contrib-developers] New <math> task implementation

[Inger, M. <Inger@Synygy.com>]

There were some limitations in the <math> task that manifested themselves
when someone tried to perform something like this:

<math result="b">
  <op op="-">
    <op op="+">
      <num value="4"/>
      <num value="2"/>
    </op>
    <num value="2"/>
  </op>
</math>

It seems the existing MathTask always kept the numerical values seperate
from the operations, and did operations (such as "-") with the numeric
values being the first operands, and not preserving the order in the xml.
Therefore the above calculation became:  2 - (4 + 2) instead of: (4+2) - 2

I have refactored (and put in their own package) the math classes so that
this doesn't happen anymore.  I will leave out the specifics of what the
refactoring involved (you can e-mail me directly if you're interested),
but part of it changed the way that Math/StrictMath methods are found and
executed.  So keep this in mind, as we have no real test cases for Math.
(anyone willing to write some if i don't have the time?)