doc: Update user guide and version numbers

This commit updates the user guide and supporting documentation to bring
it in-line with the latest v2.5.0 release. It changes the Markdown
header syntax in order to represent deeper header levels, replaces old
links and attempts to clear up areas of potential confusion with
instructions.

Change-Id: I99b464a4bc94f4618779fbe09b1aa77bed0c318e
Signed-off-by: Chris Kay <[email protected]>

Update firmware version to v2.5.0

Update firmware version to v2.5.0 and update the
documentation for the release of SCP-Firmware v2.5.0

Change-Id: Icd977b1adbffb23c1690387162a21b4266b4ff29
Signed-off-by: Ronald Cron <[email protected]>

documentation: Various fixes and improvements

Change-Id: Id4f3902985ee54530318551bdad12f4fe6481981
Signed-off-by: Ronald Cron <[email protected]>

documentation: Various fixes and improvements

Change-Id: Id4f3902985ee54530318551bdad12f4fe6481981
Signed-off-by: Ronald Cron <[email protected]>

Update firmware version to v2.4

Update firmware version to v2.4 and update the readme
file accordingly.

Change-Id: Id619c1e0efa513a96c6c5ab6038ee1b76c0ad70d
Signed-off-by: Ronald Cron <[email protected]>