Add possibility to resolve partial template specializations.

Example: The class

```
template <typename T>
class Specialization<T*> {};
```

can be accessed via

```
.. doxygenclass:: Specialization< T * >
```

The white-spaces are necessary. This changeset addresses issue #113 but is far
from being complete. Still, the argument of sphinx directives must match
exactly the doxygen XML node name including white-spaces. A better solution
is needed for that.