Rename "slave" to "replica" in documentation and command-line

Per
https://en.wikipedia.org/wiki/Master/slave_(technology)#Terminology_concerns
the use "slave" is considered offsensive in some circles.

For compatibility reasons, the "container.slave" property is
maintained, and the --slave flag is an alias for --replica.

Change-Id: If57df22705dac9450c1cf9900f051d9123d7dd2c

Documentation/dev-inspector.txt

@@ -11,7 +11,7 @@ _java_ -jar gerrit.war _daemon_
   [--enable-httpd | --disable-httpd]
   [--enable-sshd | --disable-sshd]
   [--console-log]
-  [--slave]
+  [--replica]
   -s
 --