misc: Update README/README.md (#71)

* misc: Update README to README.md

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

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>"

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

Change-Id: I18018ba23493f43861544497f23ec59f1e8debe1

---------

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

src/SConscript

@@ -615,7 +615,7 @@ PySource('m5', 'python/m5/defines.py')
 
 # Generate a file that wraps the basic top level files
 gem5py_env.Command('python/m5/info.py',
-            [ File('#/COPYING'), File('#/LICENSE'), File('#/README'),
+            [ File('#/COPYING'), File('#/LICENSE'), File('#/README.md'),
                 "${GEM5PY}", "${INFOPY_PY}" ],
             MakeAction('"${GEM5PY}" "${INFOPY_PY}" "${TARGET}" '
                        '${SOURCES[:-2]}',