create exported function for resizing disk

[baude]

libhvee should have a lib function available to resize a vhd file ...

[cfergeau]

Haven't tested the code, but it can replace what we had and compilation works cfergeau/crc@a02b912 (I think I'll develop a love/hate rship with strongunits, looks like a better docker/go-units, but with its own set of constraints to learn to work with :p )