Correct when the Processor starts using the first key

It waited for CONFIRMATIONS + 1 confirmations, instead of CONFIRMATIONS
confirmations.

Also adds a lib interface to access the coin traits and its constants.

processor/src/lib.rs

@@ -0,0 +1,7 @@
+mod plan;
+pub use plan::*;
+
+pub mod coins;
+
+mod additional_key;
+pub use additional_key::additional_key;