gluon-dns-config: update documentation (#1013)

docs/features/dns-cache.rst

 DNS-Caching
 ===========
-User experience may be greatly improved when dns is accelerated. Also it
-seems like a good idea to keep the number if packages being exchanged
+User experience may be greatly improved when dns is accelerated. Also, it
+seems like a good idea to keep the number of packages being exchanged
 between node and gateway as small as possible. In order to do this, a
 dns-cache may be used on a node. The dnsmasq instance listening on port
-53 in the node will be re-configured to answer requests, use a list of
-upstream servers and a specific cache size if the below options are
-added to site.conf All settings are optional, though if no dns server is
+53 on the node will be reconfigured to answer requests, use a list of
+upstream servers and a specific cache size if the options listed below are
+added to site.conf. All settings are optional, though if no dns server is
 set, the configuration will not be altered by gluon-core.
 
 Besides caching dns requests from clients, the next_node-addresses are set to
@@ -26,5 +26,5 @@ resolve to a configurable name that may optionally be placed in next_node.name.
   }
 
 
-The cache will be initialized during startup. Each cache entry will use roughly
-90 Bytes of main memory.
+The cache will be initialized during startup.
+Each cache entry will occupy about 90 bytes of RAM.