Enable the server to watch for filesystem changes. This patch includes
* The infrastructure for the file watching
* makes that infrastructure available to cmServerProtocols
* Resets the filesystemwatchers on "configure"

Per-source copyright/license notice headers that spell out copyright holder
names and years are hard to maintain and often out-of-date or plain wrong.
Precise contributor information is already maintained automatically by the
version control tool.  Ultimately it is the receiver of a file who is
responsible for determining its licensing status, and per-source notices are
merely a convenience.  Therefore it is simpler and more accurate for
each source to have a generic notice of the license name and references to
more detailed information on copyright holders and full license terms.

Our `Copyright.txt` file now contains a list of Contributors whose names
appeared source-level copyright notices.  It also references version control
history for more precise information.  Therefore we no longer need to spell
out the list of Contributors in each source file notice.

Replace CMake per-source copyright/license notice headers with a short
description of the license and links to `Copyright.txt` and online information
available from "https://cmake.org/licensing".  The online URL also handles
cases of modules being copied out of our source into other projects, so we
can drop our notices about replacing links with full license text.

Run the `Utilities/Scripts/filter-notices.bash` script to perform the majority
of the replacements mechanically.  Manually fix up shebang lines and trailing
newlines in a few files.  Manually update the notices in a few files that the
script does not handle.

Enable the server to send signals.

The information will be needed to send signals.

This removes some duplication and makes it easier to reuse the
vocabulary.

Tobias Hunger authored Sep 09, 2016 and Brad King committed Sep 22, 2016

Use it to split pipe and stdin/out handling out of cmServer itself.

The server will shut down when it looses its connection to the client.
This has the nice property that a crashing client will cause the server
to terminate as the OS will close the connection on behave of the client.

Enable the server to support development with some helper tools:

You can now request debug information with statistics on how
long execution of a command took, how long it took to serialize
the JSON files, and how big the serialized JSON string is.

Also allow to dump results into a file.

Pass messages sent from cmake via Error(...) or Message(...) on
to clients.

Wire up cmake::SetProgressUpdate to do progress reporting via the
cmake server.

Tobias Hunger authored Sep 09, 2016 and Brad King committed Sep 20, 2016

Allow for experimental cmProtocolVersions, which will only ever get
listed if the server was started with the (undocumented)
"--experimental" flag.

Mark current protocol version 1.0 as experimental.

Tobias Hunger authored Sep 13, 2016 and Brad King committed Sep 19, 2016

Enable the initial handshake of the client to complete the connection
to the server.

The handshake sets the protocol version that client and server will
use to talk to each other. The only way to change this is to quit the
server and start over.

CMake specific information is also set during the initial handshake.
Since cmake so far never had to change basic information about any project
while running, it was decided to keep this information static and
require a restart of the cmake server to change any of these.

Tobias Hunger authored Sep 13, 2016 and Brad King committed Sep 19, 2016

Adds a bare-bones cmake-server implementation and makes it possible
to start that with "cmake -E server".

Communication happens via stdin/stdout for now.

Protocol is based on Json objects surrounded by magic strings
("[== CMake Server ==[" and "]== CMake Server ==]"), which simplifies
Json parsing significantly.

This patch also defines an interface used to implement different
versions of the protocol spoken by the server, but does not include
any protocol implementaiton.