Move guide files to 1 folder

Moved developers' guide related files to dev_guide folder.

BUG=aomedia:2674

Change-Id: I066d00b19c64598b070f098ab34d1ab55d3b1a45

doc/dev_guide/av1_decoder.dox

diff --git a/av1_decoder.dox b/doc/dev_guide/av1_decoder.dox
similarity index 100%
rename from av1_decoder.dox
rename to doc/dev_guide/av1_decoder.dox

doc/dev_guide/av1_encoder.dox

diff --git a/av1_encoder.dox b/doc/dev_guide/av1_encoder.dox
similarity index 100%
rename from av1_encoder.dox
rename to doc/dev_guide/av1_encoder.dox

doc/dev_guide/gf_group.png

diff --git a/doc/gf_group.png b/doc/dev_guide/gf_group.png
similarity index 100%
rename from doc/gf_group.png
rename to doc/dev_guide/gf_group.png
Binary files differ

doc/dev_guide/partition.png

diff --git a/doc/partition.png b/doc/dev_guide/partition.png
similarity index 100%
rename from doc/partition.png
rename to doc/dev_guide/partition.png
Binary files differ

docs.cmake

diff --git a/docs.cmake b/docs.cmake
index 7d1e7c8..5fdc3d3 100644
--- a/docs.cmake
+++ b/docs.cmake
@@ -63,7 +63,8 @@
                                          "Bitstream inspector.")
   endif()
 
-  set(AOM_DOXYGEN_SOURCES ${AOM_DOXYGEN_SOURCES} "${AOM_ROOT}/av1_decoder.dox")
+  set(AOM_DOXYGEN_SOURCES ${AOM_DOXYGEN_SOURCES}
+                          "${AOM_ROOT}/doc/dev_guide/av1_decoder.dox")
 endif()
 
 if(CONFIG_AV1_ENCODER)
@@ -97,7 +98,8 @@
 
   set(AOM_DOXYGEN_SOURCES ${AOM_DOXYGEN_SOURCES} "${AOM_ROOT}/aom/aomcx.h"
                           "${AOM_ROOT}/usage_cx.dox")
-  set(AOM_DOXYGEN_SOURCES ${AOM_DOXYGEN_SOURCES} "${AOM_ROOT}/av1_encoder.dox")
+  set(AOM_DOXYGEN_SOURCES ${AOM_DOXYGEN_SOURCES}
+                          "${AOM_ROOT}/doc/dev_guide/av1_encoder.dox")
   set(AOM_DOXYGEN_SOURCES ${AOM_DOXYGEN_SOURCES}
                           "${AOM_ROOT}/av1/encoder/encoder.h")
 endif()
@@ -262,7 +264,7 @@
   endif()
 
   # Add image path.
-  file(APPEND "${AOM_DOXYFILE}" "IMAGE_PATH += ${AOM_ROOT}/doc\n")
+  file(APPEND "${AOM_DOXYFILE}" "IMAGE_PATH += ${AOM_ROOT}/doc/dev_guide\n")
 
   # Add the doxygen generation rule.
   add_custom_target(docs ALL