Moved some API classes into packages.

briar-api/src/org/briarproject/api/contact/ContactId.java

@@ -0,0 +1,29 @@
+package org.briarproject.api.contact;
+
+/**
+ * Type-safe wrapper for an integer that uniquely identifies a contact within
+ * the scope of a single node.
+ */
+public class ContactId {
+
+	private final int id;
+
+	public ContactId(int id) {
+		this.id = id;
+	}
+
+	public int getInt() {
+		return id;
+	}
+
+	@Override
+	public int hashCode() {
+		return id;
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (o instanceof ContactId) return id == ((ContactId) o).id;
+		return false;
+	}
+}