Increased the size of the LAYERS-column of the WmsMapLayer-class. This
way it will be possible to save strings that are larger than the default
size (of e.g. 255), which is e.g. necessary when saving a WmsMapLayer
with a long comma-separated LAYERS-argument.
Merge pull request #33 from buehner/layercolumnsize

Increased the size of the LAYERS-column of the WmsMapLayer-class