[INTERNAL] sap.ui.model.odata.type.*: constraints handling

all constraints are also accepted as string
nullable is only stored when false

PS2: rebased, TCH's review
PS3: whitespace
PS4,5: TCH's review
PS6: manually rebased due to merge conflicts

Change-Id: I85d0865b66c315c342aa0b256857bcc2f78817b4
Merge "[INTERNAL] sap.ui.model.odata.type.*: constraints handling"