Stacksmith now supports units after numbers.

Supported units are currently ticks/seconds/minutes/hours, bytes/kilobytes/megabytes/gigabytes/terabytes, but only the plural forms. We downconvert the larger value when doing maths on mixed values. Currently, physicalMemory() gives the latter units, and the download command's 'the downloads' gives the former. You can also write them in-line, like 'put 5 kilobytes + 1 megabytes'.