Add bounded limits to blocksize

Choosing 8MB because currently the consensus among miners
is 8MB is the largest tolerable size.

bip-0105.mediawiki

@@ -48,6 +48,11 @@ downvoted at no cost by the objecting hash power.
 Using difficulty as a penalty is better than a fixed cost in bitcoins because it
 is less predictable.
 
+In order to prevent miners having complete control over blocksize, an upper
+limit is required at protocol level. This feature ensures full nodes retain
+control over consensus, remembering full nodes are the mechanism to keep miners
+honest.
+
 
 ==Specification==
 
@@ -81,7 +86,7 @@ the next 2016 blocks.
 Blocks that are larger than the calculated base block size limit are invalid and
 will be rejected.
 
-The base block size limit may not reduce below 1MB.
+The base block size limit may not reduce below 1MB or increase above 8MB.
 
 
 ==Acknowledgements==