change unitOfPrice to float
add celements-subsystem-migration-manager
make document reference getter static
add migration for int unit of price field to change it to float
replace non static ioncludes of static resources by static includes
change unitOfPrice to float in test
fix a missed test and revert change to InvoiceClassCollection
Merge pull request #1 from celements/fix_allowFloatForUnitSize

Fix allow float for unit size