MEDIUM / small updates on the excel adaptors. Add the model slot
instance as well as a configuration that allows to Select or Create a
new Excel workbook. This is just a first implementation that requires
more work.
Merge branch 'excelconnector' of
ssh://git@github.com/agilebirds/openflexo into excelconnector

Conflicts:
	flexodesktop/technologyadapters/excelconnector/src/main/java/org/openflexo/technologyadapter/excel/BasicExcelModelSlotInstance.java