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/main.py

@@ -37,7 +37,7 @@ def main():
   page_template_filename = '../templates/chart_page_template.html'
   # The data files must be located in the project tree for app engine being
   # able to access them.
-  data_filenames = [ '../data/vp8_sw.py', '../data/vp8_hw.py' ]
+  data_filenames = ['../data/vp8_sw.py', '../data/vp8_hw.py']
   # Will contain info/error messages to be displayed on the resulting page.
   messages = []
   # Load the page HTML template.