Make mcuboot less mynewt style

Remove most of mynewt specific stuff to a separate port package. This
should make mcuboot less "mynewt'y" and slightly easier to port to.

- Mynewt specific stuff moved to boot/mynewt.
- Sample app moved from apps/boot to boot/mynewt.
- Use MYNEWT_VAL macro only on mynewt port.
- BOOTUTIL_* and MYNEWT_VAL() usage moved to MCUBOOT_ defines.
diff --git a/boot/mynewt/pkg.yml b/boot/mynewt/pkg.yml
new file mode 100644
index 0000000..c1c0cc7
--- /dev/null
+++ b/boot/mynewt/pkg.yml
@@ -0,0 +1,35 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+pkg.name: boot/mynewt
+pkg.type: app
+pkg.description: "Mynewt port of mcuboot"
+pkg.author: "Fabio Utzig <utzig@apache.org>"
+pkg.homepage: "http://mynewt.apache.org/"
+pkg.keywords:
+    - loader
+
+pkg.deps:
+    - "@mcuboot/boot/bootutil"
+    - "@apache-mynewt-core/kernel/os"
+    - "@apache-mynewt-core/sys/console/stub"
+
+pkg.deps.BOOT_SERIAL.OVERWRITE:
+    - "@apache-mynewt-core/sys/console/full"
+    - "@mcuboot/boot/boot_serial"