Raspberry Pi compile compatibility

This fixes 3 problems that prevent the latest repo from being compiled on a Raspberry Pi.

The cryptopp Makefile only does the Sun architecture check for x86 processors.  However, blank is considered Sun architecture.  This moves the check outside the if, so the check is always performed.  This mean Sun specific flags are not added.

The Raspbian Wheezy version of linux doesn't have a python2 link in /usr/bin.  The python link calls python 2.x.   The Makefile is updated to use python if python2 is not present.

Finally, there is an exception when starting the GUI from armoryengine.py.  /proc/cpuinfo is scanned for "model name".  However, the Raspberry doesn't have that line.  This means that the CpuStr field is left as null.

These changes allow make all to build the source files for use on the Pi.