wb_intercon: Add wb_intercon generator

wb_intercon_gen creates a verilog wrapper module that instantiates
wb_mux and wb_arbiter components to form an interconnect block.

As input, a configuration file is used for specifying masters, slaves
and their configurations.
wb_intercon: add generation of instantiation template

This make wb_intercon_gen generate a template instantiation of
the module it has created, with associated wires.
The template is generated in the form of a header file, which
is intended to be `included in the target design.
or1200-generic: use wb_intercon_gen template header file