Rename the modules and classes in webkitpy.layout_tests.servers.

It has long annoyed me that the lighttpd implementation of the web server
code was called 'http_server', and that the base class was then called
'http_server_base', even though the base class is used by the web socket
server and the crash service. This patch renames things to bring in more
sanity:

http_server -> lighttpd
apache_http_server -> apache_http
websocket_server -> pywebsocket
http_server_base -> server_base

There are no functional changes in this patch.

R=scottmg@chromium.org, ojan@chromium.org
BUG=30536

Review URL: https://codereview.chromium.org/157123002

git-svn-id: svn://svn.chromium.org/blink/trunk@166948 bbb929c8-8fbe-4397-9dbb-9b2b20218538