integrate 'construct' python library

'construct' is a declarative symmetric encoder/decoder for user
specified binary formats.  It should come in extremely handy in
tools like pySim.

We start the integration by adding transport methods for transceiving
APDUs with built-in encoding of the command data and decoding of the
response data.

Change-Id: Ibf457aa8b9480a8db5979defcfafd67674303f6c
diff --git a/docs/library.rst b/docs/library.rst
index 656a780..e2e24a7 100644
--- a/docs/library.rst
+++ b/docs/library.rst
@@ -73,6 +73,14 @@
 .. automodule:: pySim.transport.serial
    :members:
 
+
+pySim construct utilities
+-------------------------
+
+.. automodule:: pySim.construct
+   :members:
+
+
 pySim utility functions
 -----------------------