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/syscfg.yml b/boot/mynewt/syscfg.yml
new file mode 100644
index 0000000..de4f190
--- /dev/null
+++ b/boot/mynewt/syscfg.yml
@@ -0,0 +1,50 @@
+# 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.
+#
+
+# Package: boot/mynewt
+
+syscfg.defs:
+    BOOT_LOADER:
+        description: 'Set to indicate that this app is a bootloader.'
+        value: 1
+    BOOT_SERIAL:
+        description: 'Support image upgrade over serial within bootloader'
+        value: 0
+    BOOTUTIL_VALIDATE_SLOT0:
+        description: 'Validate image at slot 0 on each boot.'
+        value: 0
+    BOOTUTIL_SIGN_RSA:
+        description: 'Images are signed using RSA2048.'
+        value: 0
+    BOOTUTIL_SIGN_EC:
+        description: 'Images are signed using ECDSA NIST P-224.'
+        value: 0
+    BOOTUTIL_SIGN_EC256:
+        description: 'Images are signed using ECDSA NIST P-256.'
+        value: 0
+    BOOTUTIL_USE_MBED_TLS:
+        description: 'Use mbed TLS for crypto operations.'
+        value: 0
+    BOOTUTIL_USE_TINYCRYPT:
+        description: 'Use tinycrypt for crypto operations.'
+        value: 0
+
+syscfg.vals:
+    SYSINIT_CONSTRAIN_INIT: 0
+    OS_SCHEDULING: 0
+    OS_CPUTIME_TIMER_NUM: -1