Added webui_url to FrameworkInfo and web UI.

Allows frameworks to register a URL to its web UI.

Review: https://reviews.apache.org/r/26125
Replace some asserts with CHECKs in dispatch.

Review:
Added TCP RTT statistics for port mapping network isolator.

Review: https://reviews.apache.org/r/26090
Converted diagnosis socket Info to a struct.

Review: https://reviews.apache.org/r/26290
Moved Mesos version from mesos.hpp to version.hpp.

This allows the Module subsystem to simply include <mesos/version.hpp>
instead of inheriting the whole protobuf header chain.

Review: https://reviews.apache.org/r/26303
Install Python libraries during make install.

Because eggs are impossible to uninstall, pip + wheel has been added
as a packaging format. The wheels are generated in addition to eggs
and then subsequently installed/uninstalled.

Note that the building of eggs has not been removed. This is because
wheels cannot be run in place like eggs are via. modification of
PYTHONPATH. The eggs are needed for all the test scripts to run
correctly without actually installing anything locally.

Review: https://reviews.apache.org/r/24264
Added functionality to create SVN based diffs of arbitrary strings.

See summary.

Note that this hard codes the location of the subversion and Apache Portable Runtime (APR) headers.

Review: https://reviews.apache.org/r/24535
Added DIFF to the replicated log state storage implementation.

See summary.

Note that this hard codes the location of the subversion and Apache Portable Runtime (APR) headers.

Review: https://reviews.apache.org/r/24536
Updated metrics::Timer::stop to return elapsed time.

See summary.

Review: https://reviews.apache.org/r/24537
Add build config for svn and apr libraries