There is a need to provide convenient function which allows to slice
user data into objects to be stored in NeoFS. The main challenge is to
produce objects compliant with the format described in the NeoFS
Specification.
Add `object/slicer` package. Export `Slicer` type which performs data
slicing.
Refs #342.
Signed-off-by: Leonard Lyubich <leonard@morphbits.io>
