s/_StorableBatchSelectionDialog/_BatchSlectionDialog/

Rename the base class to match it's children common name. The 'Storable' part
and the 'Editor' part at the glade file were left overs from the development.

Change-Id: If59fd59553fe103477c9178693d24ef32dd8bc01
Merge "s/_StorableBatchSelectionDialog/_BatchSlectionDialog/"