Changed recipe_modules base paths to be abstract entities in their own right.

scripts/slave/recipes/webrtc/chromium.expected/chromium_webrtc_fyi_Win_Builder.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]\\scripts\\slave\\kill_processes.py"
     ],
     "name": "taskkill"
   },
   {
@@ skipping 67 matching lines @@
       "@@@SET_BUILD_PROPERTY@got_revision_cp@\"refs/heads/master@{#120644}\"@@@",
       "@@@SET_BUILD_PROPERTY@got_webkit_revision_cp@\"refs/heads/master@{#124383}\"@@@",
       "@@@SET_BUILD_PROPERTY@got_libjingle_revision_cp@\"refs/heads/master@{#134440}\"@@@",
       "@@@SET_BUILD_PROPERTY@got_chromium_revision_cp@\"refs/heads/master@{#170242}\"@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[BUILD]\\scripts\\slave\\recipe_modules\\webrtc\\resources\\cleanup_files.py",
+      "RECIPE_MODULE[webrtc]\\resources\\cleanup_files.py",
       "[SLAVE_BUILD]\\src\\out"
     ],
     "name": "clean test output files"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]\\scripts\\slave\\cleanup_temp.py"
     ],
@@ skipping 76 matching lines @@
       "--build_revision",
       "0f90628433546e61d9268596da93418c623137f4",
       "--factory-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"buildername\": \"Win Builder\", \"buildnumber\": 571, \"mastername\": \"chromium.webrtc.fyi\", \"parent_buildername\": null, \"recipe\": \"webrtc/chromium\", \"revision\": \"12345\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}",
       "--build-properties",
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"buildername\": \"Win Builder\", \"buildnumber\": 571, \"mastername\": \"chromium.webrtc.fyi\", \"parent_buildername\": null, \"recipe\": \"webrtc/chromium\", \"revision\": \"12345\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}"
     ],
     "name": "package build"
   }
 ]