fix isim target (remove 'simulate')
lint: add color, recursive include, Xilinx primitives

All subdirectories below ./hdl are now added to the lint search path.
%Error and %Warning get colorized.
Xilinx Unisim primitives use empty template definitions; errors in this
file are ignored using a verilator config file.
remove duplicate 'make help' entry
better 'make help' header
add default/generic bitconf file
re-order Makefile inclues
verilog indentation style cleanup