Add and use a DISALLOW_COPY_AND_ASSIGN macro.

Macro taken from the Google C++ style guide. Used on interfaces and classes
with pointers or other copiable single-owner resources (such as file
descriptors).
Move the CTLogManager class into its own file.

Some minor refactorings done at the same time, like using boost::scoped_ptr,
and making it non-copyable.
Prevent instantiating some static-only classes.
Fix using json_wrapper.h from more than one file.
Split off the HTTP handler into its own file.
Hook up SIGINT/SIGTERM to attempt a clean shutdown.
Rename the typedef for the HTTP server.
Fix a bug in client/ct on 32-bit systems.

Exhibited itself as a "STH has bad timestamp" error. See this thread for more
information:

https://groups.google.com/d/topic/certificate-transparency/Qlp7avuDzLM/discussion
Add ldns and ant to dependencies in README (and add myself as a contributor)

Signed-off-by: Katriel Cohn-Gordon <katriel.cohn-gordon@cybersecurity.ox.ac.uk>
Add get entries functionality to HttpLogClient.
Load the private key only once.
Adding a thread pool class.
Simplify AsioRepeatedEvent into RepeatingCallback.
Enable Travis caching of APT packages.
Remove "using" statements from headers.
Fix a spacing mistake in thread_pool.{h,cc}.
Remove the unused Frontend::QueueEntry method.
Remove unused methods of CertSubmissionHandler.
Remove the experimental blob server.
Update link for Protocol Buffers project.

The Google Code page indicates they've moved to Github.