AMTREDOFILE - Determine if file should be redone

Usage

doit=amtredofile(filename,mode);

amtredofile(file,mode) returns 1 if the file should be redone, based on the setting described in mode, otherwise is returns 0.

mode may one of the following flags:

`'autorefresh'`	Re-calculate the file if it does not exist. Return 1 if the file exist, otherwise 0. This is the default
`'refresh'`	Always recalculate the file.
`'cached'`	Always use the cached version. Throws an error if the file does not exist.