CACHE: Stata module to cache all other Stata commands

The cache command allows for all output and returned elements of any commands to be saved (cached), and reloaded in the future without re-running the command. When cache is used, it will check if the indicated command has been previously issued and cached by the user, and if so reload all elements returned by the command, along with command output, without re-running the command itself. Otherwise, if no previously cached result for the command exists, cache will run the command, and cache all output and returns for future uses. cache is useful if slow or resource-intensive commands are run more than once, as after the first time they are run all output can be simply accessed from the previously saved version, saving on all processing time. cache works with all valid Stata commands and is issued as a prefix before the desired command. cache stores all command output for the future, or loads all elements returned or otherwise altered by the command including (where relevant): elements accessible after the command in the ereturn, sreturn or return lists; graphical output; any alterations to data (unless nodata is specified); any alterations to frames (unless nodata is specified).