Introduce cmake-based rewrite of KBuild

Introducing CMake is an important step in a larger effort to make
Zephyr easy to use for application developers working on different
platforms with different development environment needs.

Simplified, this change retains Kconfig as-is, and replaces all
Makefiles with CMakeLists.txt. The DSL-like Make language that KBuild
offers is replaced by a set of CMake extentions. These extentions have
either provided simple one-to-one translations of KBuild features or
introduced new concepts that replace KBuild concepts.

This is a breaking change for existing test infrastructure and build
scripts that are maintained out-of-tree. But for FW itself, no porting
should be necessary.

For users that just want to continue their work with minimal
disruption the following should suffice:

Install CMake 3.8.2+

Port any out-of-tree Makefiles to CMake.

Learn the absolute minimum about the new command line interface:

$ cd samples/hello_world
$ mkdir build && cd build
$ cmake -DBOARD=nrf52_pca10040 ..

$ cd build
$ make

PR: zephyrproject-rtos#4692
docs: http://docs.zephyrproject.org/getting_started/getting_started.html

Signed-off-by: Sebastian Boe <sebastian.boe@nordicsemi.no>

subsys/bluetooth/host/CMakeLists.txt

@@ -0,0 +1,56 @@
+zephyr_library()
+zephyr_library_link_libraries(subsys__bluetooth)
+
+zephyr_library_sources_ifdef(CONFIG_BT_HCI_RAW          hci_raw.c)
+zephyr_library_sources_ifdef(CONFIG_BT_DEBUG_MONITOR    monitor.c)
+zephyr_library_sources_ifdef(CONFIG_BT_TINYCRYPT_ECC    hci_ecc.c)
+zephyr_library_sources_ifdef(CONFIG_BT_INTERNAL_STORAGE storage.c)
+zephyr_library_sources_ifdef(CONFIG_BT_A2DP             a2dp.c)
+zephyr_library_sources_ifdef(CONFIG_BT_AVDTP            avdtp.c)
+zephyr_library_sources_ifdef(CONFIG_BT_RFCOMM           rfcomm.c)
+
+zephyr_library_sources_ifdef(
+  CONFIG_BT_BREDR
+  keys_br.c
+  l2cap_br.c
+  sdp.c
+  )
+
+zephyr_library_sources_ifdef(
+  CONFIG_BT_HFP_HF
+  hfp_hf.c
+  at.c
+  )
+
+if(CONFIG_BT_HCI_HOST)
+  zephyr_library_sources(
+    uuid.c
+    hci_core.c
+    )
+  zephyr_library_sources_ifdef(
+    CONFIG_BT_HOST_CRYPTO
+    crypto.c
+    )
+
+  if(CONFIG_BT_CONN)
+    zephyr_library_sources(
+      conn.c
+      l2cap.c
+      att.c
+      gatt.c
+      )
+
+    if(CONFIG_BT_SMP)
+      zephyr_library_sources(
+        smp.c
+        keys.c
+        )
+    else()
+      zephyr_library_sources(
+        smp_null.c
+        )
+    endif()
+  endif()
+endif()
+
+add_subdirectory_ifdef(CONFIG_BT_MESH mesh)