Implement EF.ARR (Access Rule Reference) decoding

The Access Mode (AM) and Security Condition (SC) DOs are incredibly
convoluted, so we need a lot of code to properly decode them.

Change-Id: If4f0725a849d41fd93de327ed00996d8179f2b0e
diff --git a/requirements.txt b/requirements.txt
index 6da27cc..6e8336c 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,3 +4,4 @@
 cmd2
 jsonpath-ng
 construct
+bidict