[doc] Completely replace docgen with hugo

This change completely replaces docgen and replaces or removes
docgen-specific markdown in documentation.  It also does the following:

  * Updates all local links to use hugo relative references so that a
    broken link is a broken build.
  * Uses upstream wavedrom, which breaks at least one page that depends
    on local modifications.
  * Renames most hw/ip/**/ip_name.doc and dv_plan documents for a more
    aesthetic document tree layout.
  * Moves some doc/ pages into their own page bundle.
  * Updates util/build_docs.py to pre-generate registers, hwcfg, and
    dashboard fragments and invoke hugo.
diff --git a/doc/ug/getting_started_sw.md b/doc/ug/getting_started_sw.md
index d4b0c7c..fe3a52b 100644
--- a/doc/ug/getting_started_sw.md
+++ b/doc/ug/getting_started_sw.md
@@ -2,7 +2,7 @@
 
 ## Prerequisites
 
-_Make sure you followed the install instructions to [prepare the system](install_instructions.html#system-preparation) and install the [compiler toolchain](install_instructions.html#compiler-toolchain)._
+_Make sure you followed the install instructions to [prepare the system]({{< relref "install_instructions#system-preparation" >}}) and install the [compiler toolchain]({{< relref "install_instructions#compiler-toolchain" >}})._
 
 ## Building software
 
@@ -18,4 +18,4 @@
 * `.dis`: the disassembled program
 * `.vmem`: a Verilog memory file which can be read by `$readmemh()` in Verilog code
 
-Please see [SW build flow](../../sw/doc/sw_build_flow.md) for more details.
+Please see [SW build flow]("/sw/doc/sw_build_flow.md") for more details.