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}
diff --git a/webrtc/build/android/test_runner.py b/webrtc/build/android/test_runner.py
index 6169bbc..2fec37c 100755
--- a/webrtc/build/android/test_runner.py
+++ b/webrtc/build/android/test_runner.py
@@ -25,7 +25,7 @@
 sys.path.insert(0, CHROMIUM_BUILD_ANDROID_DIR)
 
 
-import test_runner
+import test_runner  # pylint: disable=W0406
 from pylib.gtest import gtest_config
 from pylib.gtest import setup