Move CMakeLists.txt files (other than the one in the repository root)

and the cmake directory into a new directory ``contrib/cmake`` that
mirrors the directory structure of the root. This is a comprimise
between me and Christoph Wintersteiger that was suggested by Arie
Gurfinkel that allows the CMake build system to live in the Z3
repository but not impact the Z3 developers that want to avoid the CMake
build system. The build system will not work in its new location
and a bootstrap script will soon be provided that allows a developer
to copy the files back to their correct location.

contrib/cmake/src/cmd_context/CMakeLists.txt

@@ -0,0 +1,21 @@
+z3_add_component(cmd_context
+  SOURCES
+    basic_cmds.cpp
+    check_logic.cpp
+    cmd_context.cpp
+    cmd_context_to_goal.cpp
+    cmd_util.cpp
+    context_params.cpp
+    echo_tactic.cpp
+    eval_cmd.cpp
+    interpolant_cmds.cpp
+    parametric_cmd.cpp
+    pdecl.cpp
+    simplify_cmd.cpp
+    tactic_cmds.cpp
+    tactic_manager.cpp
+  COMPONENT_DEPENDENCIES
+    interp
+    rewriter
+    solver
+)

contrib/cmake/src/cmd_context/extra_cmds/CMakeLists.txt

@@ -0,0 +1,10 @@
+z3_add_component(extra_cmds
+  SOURCES
+    dbg_cmds.cpp
+    polynomial_cmds.cpp
+    subpaving_cmds.cpp
+  COMPONENT_DEPENDENCIES
+    arith_tactics
+    cmd_context
+    subpaving_tactic
+)