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/video_processing/BUILD.gn

@@ -54,7 +54,9 @@ source_set("video_processing") {
 
 if (build_video_processing_sse2) {
   source_set("video_processing_sse2") {
-    sources = [ "main/source/content_analysis_sse2.cc" ]
+    sources = [
+      "main/source/content_analysis_sse2.cc",
+    ]
 
     configs += [ "../..:common_config" ]
     public_configs = [ "../..:common_inherited_config" ]