[FIX] simplified EmpiricalFormula

Removed some methods takings String arguments that blew up the interface.
doesnt one imply the other? if it is empty, there should also be no charge?

this should be a class invariant, e.g. there cannot be a charge set if
there are no elements in the formula!

On 13 September 2014 09:34, Timo Sachsenberg <notifications@github.com>
wrote:

> In src/openms/source/CHEMISTRY/ResidueModification.cpp:
>
> > @@ -508,7 +508,7 @@ namespace OpenMS
> >
> >    bool ResidueModification::hasNeutralLoss() const
> >    {
> > -    return neutral_loss_diff_formula_ != "";
> > +    return neutral_loss_diff_formula_.toString() != "";
>
> note: there is isEmpty() and isCharged(). Maybe having a general empty()
> thats tests for no elements and zero charge would make sense?
>
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