docs: moving code examples

Code now resides in `docs/source/code_examples`.
`CHAPTER_Prog` -> `stubnets`
`APPNOTE_011_Design_Investigation` -> `selections` and `show`
`resources/PRESENTATION_Intro` -> `intro`
`resources/PRESENTATION_ExSyn` -> `synth_flow`
`resources/PRESENTATION_ExAdv` -> `techmap`,  `macc`, and `selections`
`resources/PRESENTATION_ExOth` -> `scrambler` and `axis`

Note that generated images are not yet configured to build from the new code locations.

docs/source/code_examples/scrambler/Makefile

@@ -0,0 +1,8 @@
+PROGRAM_PREFIX :=
+
+YOSYS ?= ../../../$(PROGRAM_PREFIX)yosys
+
+all: scrambler_p01.dot scrambler_p02.dot
+
+scrambler_p01.dot scrambler_p02.dot: scrambler.ys scrambler.v
+	$(YOSYS) scrambler.ys

docs/source/code_examples/scrambler/scrambler.v

@@ -0,0 +1,14 @@
+module scrambler(
+        input clk, rst, in_bit,
+        output reg out_bit
+);
+    reg [31:0] xs;
+    always @(posedge clk) begin
+    	if (rst)
+	    xs = 1;
+        xs = xs ^ (xs << 13);
+        xs = xs ^ (xs >> 17);
+        xs = xs ^ (xs << 5);
+        out_bit <= in_bit ^ xs[0];
+    end
+endmodule

docs/source/code_examples/scrambler/scrambler.ys

@@ -0,0 +1,22 @@
+read_verilog scrambler.v
+
+hierarchy; proc;;
+
+cd scrambler
+submod -name xorshift32 xs %c %ci %D %c %ci:+[D] %D %ci*:-$dff xs %co %ci %d
+cd ..
+
+show -prefix scrambler_p01 -format dot -notitle scrambler
+show -prefix scrambler_p02 -format dot -notitle xorshift32
+
+echo on
+
+cd xorshift32
+rename n2 in
+rename n1 out
+
+eval -set in 1 -show out
+eval -set in 270369 -show out
+
+sat -set out 632435482
+