Add script to convert units to a base value.

[dvalinrh]

We need a tool that given a unit value and value, will convert to another unit. This is required because

1. Multiple runs of the same benchmark can results in different units being provided.
2. The ability to show the results of a benchmark always in the same unit.
3. This spans multiple benchmarks, so a generic solution is required.

Given a unit, convert it to the base.
Time base is nano seconds
Memory base is bytes

There is an existing program, numfmt that provides the units for us, so instead of duplicating each functionality we will leverage it. Also we do not want to duplicate the required logic in every wrapper, so we create a generic script.

To differentiate between time and a 10 based measurement we will symlink a well known script name that is for time. We check $0 on execution of the script if it is the time symlink, then we know we are dealing with time values, and act accordingly.

[kdvalin]

I think there's a better way to differentiate between time conversion and normal unit conversion than what the running script name is.

[kdvalin]

Minor nits

[kdvalin]

LGTM