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}

tools/python_charts/webrtc/data_helper_test.py

@@ -18,7 +18,7 @@ class Test(unittest.TestCase):
                          {'frame_number': 1, 'ssim': 0.55, 'psnr': 30.55}]
     self.frame_data_1 = [{'frame_number': 0, 'ssim': 0.6, 'psnr': 30.6},
                          {'frame_number': 0, 'ssim': 0.66, 'psnr': 30.66}]
-    self.all_data = [ self.frame_data_0, self.frame_data_1 ]
+    self.all_data = [self.frame_data_0, self.frame_data_1]
 
     # Test with frame_number column in a non-first position sice we need to
     # support reordering that to be able to use the gviz_api as we want.