[KARAF-2511] Review and update the developer commands page of the developers guide
[KARAF-2511] Review and update the scripting page of the developers guide
[KARAF-2511] Review and update the connect page of the developers guide
[KARAF-2511] Review and update the branding page of the developers guide
[KARAF-2511] Update the developers guide toc
Add README for system dir