Construct a machineType URL

gce_make_machinetype_url(predefined_type = NULL, cpus = NULL,
memory = NULL, zone = gce_get_global_zone())

## Arguments

predefined_type A predefined machine type from gce_list_machinetype If not defining predefined_type, the number of CPUs If not defining predefined_type, amount of memory zone for URL

## Value

A url for use in instance creation

## Details

cpus must be in multiples of 2 up to 32 memory must be in multiples of 256