Applying the snake_case convention throughout the repo (#967)

* Applying the snake_case convention throughout the repo

- Also removing the file extension where not needed
- Adding {{ }} on a few old pages

* Addressing concerns

- Added {{ }} where they were missed out
- Removed spaces inside {{ }}
- Reverting "file" to "filename" to make it clearer

* Fixing the comments on nc page

pages/linux/mdadm.md

@@ -4,7 +4,7 @@
 
 - Create array:
 
-`mdadm --create {{/path/to/raid_device_file}} --level {{ raid level }} --raid-devices {{ number of disks}} {{/path/to/disk_device_file}}`
+`mdadm --create {{/path/to/raid_device_file}} --level {{raid_level}} --raid-devices {{number_of_disks}} {{/path/to/disk_device_file}}`
 
 - Stop array: