Show directories and files with most warnings.

* Now with 4 sections that can be shown/hidden independently.
* After the 'selected_projects' section, add two more sections:
  * 'top_directory_section' contains
    * a table of directories with at least 1% warnings.
    * a 'selected_directory_warnings' subsection to show all warnings
      in the clicked directory from the directory table
  * 'top_file_section' contains
    * a table of files with at least 100 or 1% warnings.
    * a 'selected_file_warnings' subsection to show all warnings
      in the clicked file from the file table
* Adjust button/section spaces and reduce button font size to 100%.
* Rename drawTable to genTables.

Test: warn.py --url=http://cs/android --separator='?l=' build.log > warnings.html
Test: warn.py --gencsv build.log > warnings.csv
Change-Id: I765b09a46adc111cfe781719ba7aa0f917aa6ffc