Added Avalon support to wb_intercon_gen

Refactored code and introduced 'bustype=avalon' as well.

Bonus commit: Added clk/rst to bus converter logics.
Update wb_avalon_bridge for wb_intercon_gen

Renames port on wb_avalon_bridge to match those generated in
wb_intercon_gen. This also changes the view of the port to be an "input
master" to a "slave" port, which is functionally equivalent.