Major renaming and refactoring in activity and service

Apparently "configuration" is the proper term, not "profile".

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

app/src/main/java/com/wireguard/config/Interface.java

@@ -12,13 +12,29 @@ import com.wireguard.crypto.KeyEncoding;
  * Represents the configuration for a WireGuard interface (an [Interface] block).
  */
 
-public class Interface extends BaseObservable implements Observable {
+public class Interface extends BaseObservable implements Copyable<Interface>, Observable {
     private String address;
     private String dns;
     private String listenPort;
     private Keypair keypair;
     private String mtu;
 
+    @Override
+    public Interface copy() {
+        final Interface copy = new Interface();
+        copy.copyFrom(this);
+        return copy;
+    }
+
+    @Override
+    public void copyFrom(final Interface source) {
+        address = source.address;
+        dns = source.dns;
+        listenPort = source.listenPort;
+        keypair = source.keypair;
+        mtu = source.mtu;
+    }
+
     public void generateKeypair() {
         keypair = new Keypair();
         notifyPropertyChanged(BR.privateKey);
@@ -55,7 +71,7 @@ public class Interface extends BaseObservable implements Observable {
         return keypair != null ? keypair.getPublicKey() : null;
     }
 
-    public void parseFrom(String line) {
+    public void parseFrom(final String line) {
         final Attribute key = Attribute.match(line);
         if (key == Attribute.ADDRESS)
             address = key.parseFrom(line);
@@ -67,29 +83,39 @@ public class Interface extends BaseObservable implements Observable {
             mtu = key.parseFrom(line);
         else if (key == Attribute.PRIVATE_KEY)
             keypair = new Keypair(key.parseFrom(line));
+        else
+            throw new IllegalArgumentException(line);
     }
 
     public void setAddress(String address) {
+        if (address != null && address.isEmpty())
+            address = null;
         this.address = address;
         notifyPropertyChanged(BR.address);
     }
 
     public void setDns(String dns) {
+        if (dns != null && dns.isEmpty())
+            dns = null;
         this.dns = dns;
         notifyPropertyChanged(BR.dns);
     }
 
     public void setListenPort(String listenPort) {
+        if (listenPort != null && listenPort.isEmpty())
+            listenPort = null;
         this.listenPort = listenPort;
         notifyPropertyChanged(BR.listenPort);
     }
 
     public void setMtu(String mtu) {
+        if (mtu != null && mtu.isEmpty())
+            mtu = null;
         this.mtu = mtu;
         notifyPropertyChanged(BR.mtu);
     }
 
-    public void setPrivateKey(String privateKey) {
+    public void setPrivateKey(final String privateKey) {
         if (privateKey != null && !privateKey.isEmpty()) {
             // Avoid exceptions from Keypair while the user is typing.
             if (privateKey.length() != KeyEncoding.KEY_LENGTH_BASE64)