Doxygen improvements to improve documentation of C API (rapidsai#2355)

Some doxygen improvements:
 * Defined a C API module
 * Defined submodules for each C API algorithm header
 * Moved sampling functions into a separate header
 * Moved traversal functions into a separate header
 * Deleted a few old nvgraph doxygen things that were interfering with a clean definition of the cugraph namespace

Authors:
  - Chuck Hastings (https://github.com/ChuckHastings)

Approvers:
  - Brad Rees (https://github.com/BradReesWork)
  - AJ Schmidt (https://github.com/ajschmidt8)

URL: rapidsai#2355

ci/release/update-version.sh

@@ -62,7 +62,7 @@ for FILE in conda/environments/*.yml; do
 done
 
 # Doxyfile update
-sed_runner "s|\(TAGFILES.*librmm/\).*|\1${NEXT_SHORT_TAG}|" cpp/doxygen/Doxyfile
+sed_runner "s|PROJECT_NUMBER[[:space:]]*=.*|PROJECT_NUMBER=${NEXT_SHORT_TAG}|" cpp/doxygen/Doxyfile
 
 # ucx-py version
 sed_runner "s/export UCX_PY_VERSION=.*/export UCX_PY_VERSION='${NEXT_UCX_PY_VERSION}'/g" ci/benchmark/build.sh

cpp/doxygen/Doxyfile

@@ -38,13 +38,13 @@ PROJECT_NAME           = "libcugraph"
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = 0.14
+PROJECT_NUMBER         = 22.08
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewer a
 # quick idea about the purpose of the project. Keep the description short.
 
-PROJECT_BRIEF          =
+PROJECT_BRIEF          = GPU accelerated graph analytics
 
 # With the PROJECT_LOGO tag one can specify a logo or an icon that is included
 # in the documentation. The maximum height of the logo should not exceed 55

cpp/include/cugraph/algorithms.hpp

@@ -30,6 +30,10 @@
 #include <raft/random/rng_state.hpp>
 #include <raft/span.hpp>
 
+/** @ingroup cpp_api
+ *  @{
+ */
+
 namespace cugraph {
 
 /**
@@ -1572,3 +1576,7 @@ void triangle_count(raft::handle_t const& handle,
                     bool do_expensive_check = false);
 
 }  // namespace cugraph
+
+/**
+ * @}
+ */

cpp/include/cugraph/graph.hpp

@@ -28,6 +28,10 @@
 #include <type_traits>
 #include <vector>
 
+/** @defgroup cpp_api cuGraph C++ API
+ *  @{
+ */
+
 namespace cugraph {
 
 template <typename vertex_t, typename edge_t, typename weight_t>
@@ -551,3 +555,7 @@ __host__ __device__ std::enable_if_t<std::is_unsigned<vertex_t>::value, bool> is
 }  // namespace cugraph
 
 #include "eidecl_graph.hpp"
+
+/**
+ * @}
+ */