XSI-1385: Collect plain text (human-readable) SAR file reports

[bernhardkaindl]

XSI-1385: Add plain-text reports of sar data

Software Support's Lead Escalation Engr in Chiyoda-ku escalated the need for human-readable plain-text sar data and contributed this implementation

Problem: To read the binary sar data, the same sysstat version is needed to parse it, which can be an obstacle.

• Collect the daily sar reports created by by sa2 each day at 23:53.
• Collect a report of the sar data of the current day so far.

The current version of sadf from https://github.com/sysstat can even generate reports in even more data formats, but our current version appears to support JSON already, so extending it to collect the SAR data in JSON format looks like a logical next step.

[bernhardkaindl]

@andyhhp @lindig I've incorporated and answered your review comments, ready for further review again!

[bernhardkaindl]

@rosslagerwall This (human readable sar files) is the 1st PR which I'd like to merge:

Andrew approved it, Christian also took a look at it, do you like to review it?