Remodel the Model

- The configuration and crypto model is now entirely independent
of Android classes other than Nullable and TextUtils.
- Model classes are immutable and use builders that enforce the
appropriate optional/required attributes.
- The Android config proxies (for Parcelable and databinding) are
moved to the Android side of the codebase, and are designed to be
safe for two-way databinding. This allows proper observability in
TunnelDetailFragment.
- Various robustness fixes and documentation updates to helper classes.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

.idea/copyright/Default.xml

@@ -1,6 +1,6 @@
 <component name="CopyrightManager">
   <copyright>
-    <option name="notice" value="Copyright © &amp;#36;today.year Firstname Lastname &lt;email@example.org&gt;&#10;SPDX-License-Identifier: Apache-2.0
+    <option name="notice" value="Copyright © &amp;#36;today.year WireGuard LLC. All Rights Reserved.&#10;SPDX-License-Identifier: Apache-2.0" />
     <option name="myName" value="Default" />
   </copyright>
 </component>

.idea/copyright/profiles_settings.xml

@@ -1,3 +1,3 @@
 <component name="CopyrightManager">
-  <settings default="GPL-2.0-or-later" />
-</component>
+  <settings default="Default" />
+</component>