Pre-compile metrics at build time.

[coleramos425]

Describe the suggestion
Pre-compile metrics at build time.

Justification
Metric compilation leads to a huge overhead in the analyze step (both on the CLI and standalone GUI). Further, the metrics themselves typically are unchanging for a given version after install (e.g., it's an experts-only thing to do). Therefore, we would greatly benefit from the ability to 'compile' the metrics are build/install time, such that they we can swap many, many calls to eval for loading a pre-compiled python module (say).

Implementation
I'm sure Fei has better ideas than me here, but one option would be to simply parse the metric and generate a corresponding python function to evaluate it (e.g., everything inside of the 'AVG', 'MAX', 'MIN', etc.). This can then be applied row-wise to a data-frame using apply. If needed, we could put all counter values into e.g., a row['<counter name>'] or some other uniform name for the row that can be passed to the function.

Additional Notes

Also, we should drop the separate metrics for 'AVG' v 'MIN' v 'MAX', etc., and just rely on pandas functions for these to cut down on unnecessary function calls / evals.

cc: @feizheng10

Originally posted by @arghdos in #153 (comment)