Update bitcoin.conf with example for pruning

This option is becoming more popular recently, and I propose an example to be shown in the bitcoin.conf.

pruning comments

updated and corrected pruning comments

Revised details on pruning in bitcoin.conf

Revised details on pruning in bitcoin.conf

spelling and space

spelling and space

add details on pruning in bitcoin.conf

contrib/debian/examples/bitcoin.conf

@@ -131,6 +131,13 @@
 # be validated sooner.
 #paytxfee=0.00
 
+# Enable pruning to reduce storage requirements by deleting old blocks. 
+# This mode is incompatible with -txindex and -rescan.
+# 0 = default (no pruning).
+# 1 = allows manual pruning via RPC.
+# >=550 = target to stay under in MiB. 
+#prune=550
+
 # User interface options
 
 # Start Bitcoin minimized