Testnet2 small fixes (#899)

* add hint for gcc-5 for building CUDA plugin
* add N_BLOCks comment for >=6GB GPU cards
* minor logging cleanup
* mark to be kept + reformat as "@ height [hash]"
* show CuckooNN + better wording

core/src/core/block.rs

@@ -414,7 +414,7 @@ impl Block {
 	/// Hydrate a block from a compact block.
 	/// Note: caller must validate the block themselves, we do not validate it here.
 	pub fn hydrate_from(cb: CompactBlock, txs: Vec<Transaction>) -> Block {
-		debug!(
+		trace!(
 			LOGGER,
 			"block: hydrate_from: {}, {} txs",
 			cb.hash(),