Add protocol choice

Signed-off-by: John Else <john.else@citrix.com>
Add xenstore client

Signed-off-by: John Else <john.else@citrix.com>
add test plugin

Signed-off-by: John Else <john.else@citrix.com>
rrdd plugins should exit on SIGTERM/SIGINT

Otherwise the main loop catches the EINTR and continues running,
and the init script eventually has to send SIGKILL.

Signed-off-by: John Else <john.else@citrix.com>
Add generic plugin cleanup function

Signed-off-by: John Else <john.else@citrix.com>
Remove redundant handling of Sys.Break

It's already handled by the main loop.

Signed-off-by: John Else <john.else@citrix.com>
Add interdomain version of the main loop

Signed-off-by: John Else <john.else@citrix.com>
Add runtime mode switch to dummy plugin

Signed-off-by: John Else <john.else@citrix.com>
Tidy code

Signed-off-by: John Else <john.else@citrix.com>
Add runtime protocol switch to dummy plugin

Signed-off-by: John Else <john.else@citrix.com>