ufz/ogs — pull request #432 by rinkk (2014-08-05 13:56:03+00:00)
Title: XML numeric file reader

This is a first implementation of a file reader for an xml-numeric file, based on discussions with @endJunction, @TomFischer, @nagelt and NB.
I designed a schema-file and the reader currently only validates files according to that schema, reads the information and outputs everything that has been read (as there is to my information currently no data-holder-object for numeric information).

An example file would look like this:
```xml

Newton

BiCGStab
diagonal

10
5

L2Norm
1E-10

```

Note that implicitly every configuration is assumed to be non-linear. According to @nagelt this isn't really an issue as you could always choose ```MaxIterations=1``` for a linear problem.

Please let me know if this is basically okay or what needs changing otherwise. (Aside from various parameters that can be added later...)