Instead of always specifying segment size in bytes the user
can now use B,K,M or G as suffixes for the corresponding
size.
Conversion is done with Binary units (1024) rather than SI
units (1000).
e.g
swift upload test_container -S 1073741824 large_file
can now be written
swift upload test_container -S 1G large_file
The change is backwards compatible as it ignores arguments to -S
that don't have a valid suffix.
Updated unit tests and help message.
Change-Id: I6314b4e45cf2fbffde2fe57a02df77a25e911e84