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.py

@@ -89,7 +89,7 @@ class DataHelper(object):
     # We're going to have one dictionary per row.
     # Create that and copy frame_number values from the first data set
     for source_row in self.data_list[0]:
-      row_dict = { 'frame_number': source_row['frame_number'] }
+      row_dict = {'frame_number': source_row['frame_number']}
       result_data_table.append(row_dict)
 
     # Pick target field data points from the all data tables