Add support for forwarding cache eviction for custom caches

Allow to specify cache.pattern in the plugin configuration, which
will add additional patterns to the regex to test if a cache eviction
should be forwarded. This will allow caches created by other plugins
to be handled in addition to the default core caches.

For example:

  [cache]
    synchronize = true
    pattern = ^my_cache.*
    pattern = other_cache

Note that evictions for core caches are always forwarded. Specifying
cache.pattern only adds extra matches; it doesn't override forwarding
of eviction for the core caches.

Change-Id: Ia415d53a3c08d744324e88a6f7115a761f94c1f6

src/main/resources/Documentation/config.md

diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index 8ec9432..1ab2858 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -62,6 +62,13 @@
 :   Maximum number of threads used to send cache evictions to the target instance.
     Defaults to 1.
 
+cache.pattern
+:   Pattern to match names of custom caches for which evictions should be
+    forwarded (in addition to the core caches that are always forwarded). May be
+    specified more than once to add multiple patterns.
+    Defaults to an empty list, meaning only evictions of the core caches are
+    forwarded.
+
 event.synchronize
 :   Whether to synchronize stream events.
     Defaults to true.