Do not include replication and delete-project into the jar

The pull-replication plugin depends on the replication and
delete-project plugins, therefore should not include them in
its far-jar but rather reference them.

Also amend the documentation to reflect the dependencies.

Change-Id: I5146e93c115343b75a97c1dad9ea334362e7f844

BUILD

diff --git a/BUILD b/BUILD
index 5825e1d..9a37098 100644
--- a/BUILD
+++ b/BUILD
@@ -16,11 +16,11 @@
     ],
     resources = glob(["src/main/resources/**/*"]),
     deps = [
+        ":delete-project-neverlink",
         ":events-broker-neverlink",
         ":healthcheck-neverlink",
+        ":replication-neverlink",
         "//lib/commons:io",
-        "//plugins/delete-project",
-        "//plugins/replication",
         "@commons-lang3//jar",
     ],
 )
@@ -92,3 +92,15 @@
     neverlink = 1,
     exports = ["//plugins/healthcheck"],
 )
+
+java_library(
+    name = "replication-neverlink",
+    neverlink = 1,
+    exports = ["//plugins/replication"],
+)
+
+java_library(
+    name = "delete-project-neverlink",
+    neverlink = 1,
+    exports = ["//plugins/delete-project"],
+)

src/main/resources/Documentation/about.md

diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index 22b52e7..bfc2974 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -1,5 +1,8 @@
 This plugin can automatically mirror repositories from other systems.
 
+Overview
+--------
+
 Typically replication should be done over SSH, with a passwordless
 public/private key pair.  On a trusted network it is also possible to
 use replication over the insecure (but much faster due to no
@@ -9,6 +12,13 @@
 local path as replication source. This makes e.g. sense if a network
 share is mounted to which the repositories should be replicated from.
 
+Installation
+------------
+
+This plugin depends on the replication and delete-project plugins,
+therefore requires them to be installed as well into the
+`$GERRIT_SITE/plugins` directory.
+
 Access
 ------