Add a timestamp to netconf cache, fix some SQL queries in NC.

include/ZeroTierOne.h

@@ -103,6 +103,17 @@ extern "C" {
  */
 #define ZT1_MAX_PEER_NETWORK_PATHS 4
 
+/**
+ * Maximum number of revisions over which a network COM can differ and still be in-horizon (agree)
+ *
+ * This is the default max delta for the revision field in COMs issued
+ * by network controllers, and is defined here for documentation purposes.
+ * When a network is changed so as to de-authorize a member, its revision
+ * should be incremented by this number. Otherwise all other changes that
+ * materially affect the network should result in increment by one.
+ */
+#define ZT1_CERTIFICATE_OF_MEMBERSHIP_REVISION_MAX_DELTA 16
+
 /**
  * Feature flag: ZeroTier One was built to be thread-safe -- concurrent processXXX() calls are okay
  */