This change converts the text-based README to markdown. This works
better with modern source-control systems, most notably, GitHub.

The README.md has been broken down into sections to better organize the
document.

Change-Id: I18018ba23493f43861544497f23ec59f1e8debe1

Change-Id: I90296c69098e9bf5987c142d52ab57d556a22009

This section now included expanded information on Reporting bugs and
Requesting Features.

Change-Id: I555f9f5edb683a1ee235058045fbce07ea473138

Change-Id: Ic9174d6c3d905f85e2f7f159478d8c93ef7e4079

Due to renaming 'README' to 'README.md', this code was generating the
following for "info.py":

```
README.md = "<FILE CONTENTS HERE>"
```

As '.' is used to access member variables/methods in python. To fix this
"infopy.oy" now replaces "." with "_". As such the generated in in
"info.py" is now:

```
README_MD = "<FILE CONTENTS HERE>"

Change-Id: I834fa84f654b27ef399a31cda545d2bf2d906390

Co-authored-by: Jason Lowe-Power <jason@lowepower.com>

Change-Id: I23f204507be0908afa982712adc9ff7b6c7e8dd3
Addresss: gem5#71 (comment)

This puts GitHub Discussions and GitHub Issues towards the top of the
list. This is to incentivize their usage.

Change-Id: I248e3a5ace58bf909182300a3c44a412a8d73e6e
Addresses: gem5#71 (comment)

Change-Id: Ibfb4642768cc29a5da04ae416ff137ad8bf11b68
Addresses: gem5#71 (comment)