use boost::ptr_vector for wesnothd::game::history_
use boost::ptr_vector for wesnotd::server::games_

this way we have a prettier interface and don't have to delete them
manually.

I also had to change some functions that previously took non-null
pointer to taking referenes.
Merge pull request #340 from gfgtdf/wesnothd_sides

use boost::ptr_vector for wesnothd::game::history_
use boost::ptr_vector for wesnotd::server::games_
travis: as a test, try turning off the nogui option for play test
Revert "travis: as a test, try turning off the nogui option for play test"

This reverts commit 6bca3fa96db46908c5914b8315024344e784e882.
fix warnings about unreferenced local variable
mute MSVC warnings in a boost header
avoid MSVC warnings about macro redefinitions INADDR_ANY, -BROADCAST, -NONE
disable several 1000 boost header level 4 MSVC warnings project-wide
add plugins context, manager, create lua thread object

This collection of classes provides a framework whereby the engine
may provide scripting capabilities in any "context". A C++
function may declare a plugin context by providing a list of names
function objects, then may call "play_slice()" on this context to
transfer control to lua. A lua script may generate some arguments
and request to call some of these, then yield to the engine. C++
will run them until one of them signals an error, or that the
context is now invalid (using a boolean return value).

The intended semantics is that lua may only make requests
corresponding to the current context. As soon as a new context
is used (play_slice() is called again) the old context is invalid
from lua's point of view -- calling those functions is a lua
error but not undefined behavior. This should be the case even if
the old context has not been destroyed yet in C++, for instance
if a lua request resulted in a new context being created. There is
a system of locks in place to ensure that when old contexts are
invalidated, stale requests are discarded.

We also add the coroutine library to our lua base. This because
threads are run as coroutines, and writing them requires the use
of coroutine yield from the standard library.
add accessor functions to plugins contexts

This allows scripts to request more info from the engine.
add plugins bindings to titlescreen and mp lobby
move the "get_str" shim to the plugins/context header
add --plugin option at command line (to replace script eventually)

This is still rough and will need to be cleaned up later.
add "describe_plugins()" to the application lua kernel
allow to open the app lua kernel in the multiplayer lobby
fixup error reporting when loading a thread's script

Should use T_ not mState...
add some debugging output to plugins manager on channel "plugins"
change "get_str" plugin callback shim to make a temp string copy

This prevents a segfault when using "send chat message".
add some debugging output to check that plugins context is running