PRESUBMIT: Improve PyLint check and add GN format check.

Add pylintrc file based on
https://code.google.com/p/chromium/codesearch#chromium/src/tools/perf/pylintrc
bit tightened up quite a bit (the one in depot_tools is far
more relaxed).

Remove a few excluded directories from pylint check and fixed/
suppressed all warnings generated.

Add GN format check + formatted all GN files using 'gn format'.
Cleanup redundant rules in tools/PRESUBMIT.py

TESTED=Ran 'git cl presubmit -vv', fixed the PyLint violations.
Ran it again with a modification in webrtc/build/webrtc.gni, formatted
all the GN files and ran it again.

R=henrika@webrtc.org, phoglund@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/50069004

Cr-Commit-Position: refs/heads/master@{#9274}

webrtc/modules/bitrate_controller/BUILD.gn

@@ -24,7 +24,7 @@ source_set("bitrate_controller") {
   if (is_win) {
     cflags = [
       # TODO(jschuh): Bug 1348: fix this warning.
-      "/wd4267"  # size_t to int truncations
+      "/wd4267",  # size_t to int truncations
     ]
   }
 
@@ -37,5 +37,7 @@ source_set("bitrate_controller") {
     configs -= [ "//build/config/clang:find_bad_constructs" ]
   }
 
-  deps = [ "../../system_wrappers" ]
+  deps = [
+    "../../system_wrappers",
+  ]
 }