Removed library sources and docs; moved to Boost.Config.

This library has been merged into Boost.Config, including sources,
documentation, tests and examples. index.html updated to redirect to
Boost.Config. README.md and meta/libraries.json were updated to mention
that the library was merged into Boost.Config.

CMakeLists.txt and build.jam are retained to define Boost.StaticAssert
targets, which are now empty and only add the dependency on Boost.Config.
This is to avoid breaking downstream libraries that have Boost.StaticAssert
as a dependency. These users will need to be updated, and at that point
this entire git submodule can be deleted.

Tests, examples and CI configs are preserved at the request by Peter Dimov.

Author: Lastique

CMakeLists.txt

@@ -11,8 +11,6 @@ project(boost_static_assert VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CX
 add_library(boost_static_assert INTERFACE)
 add_library(Boost::static_assert ALIAS boost_static_assert)
 
-target_include_directories(boost_static_assert INTERFACE include)
-
 target_link_libraries(boost_static_assert
   INTERFACE
     Boost::config

README.md

@@ -4,33 +4,4 @@ Boost StaticAssert Library
 The Boost StaticAssert library provides static assertions for C++, this library is the ancestor to C++ native static_assert's and 
 can be used on older compilers which don't have that feature.
 
-The full documentation is available on [boost.org](http://www.boost.org/doc/libs/release/libs/static_assert).
-
-## Support, bugs and feature requests ##
-
-Bugs and feature requests can be reported through the [Gitub issue tracker](https://github.com/boostorg/static_assert/issues)
-(see [open issues](https://github.com/boostorg/static_assert/issues) and
-[closed issues](https://github.com/boostorg/static_assert/issues?utf8=%E2%9C%93&q=is%3Aissue+is%3Aclosed)).
-
-You can submit your changes through a [pull request](https://github.com/boostorg/static_assert/pulls).
-
-There is no mailing-list specific to Boost StaticAssert, although you can use the general-purpose Boost [mailing-list](http://lists.boost.org/mailman/listinfo.cgi/boost-users) using the tag [static_assert].
-
-
-## Development ##
-
-Clone the whole boost project, which includes the individual Boost projects as submodules ([see boost+git doc](https://github.com/boostorg/boost/wiki/Getting-Started)): 
-
-    git clone https://github.com/boostorg/boost
-    cd boost
-    git submodule update --init
-
-The Boost StaticAssert Library is located in `libs/static_assert/`. 
-
-### Running tests ###
-First, make sure you are in `libs/static_assert/test`. 
-You can either run all the tests listed in `Jamfile.v2` or run a single test:
-
-    ../../../b2                        <- run all tests
-    ../../../b2 static_assert_test     <- single test
-
+This library has been merged into [Boost.Config](https://github.com/boostorg/config). The full documentation is available on [boost.org](https://www.boost.org/doc/libs/release/libs/config).