Added new convenience class Nowish to always give a unique timestamp,…

… even if it's not 100% accurate

core/src/main/scala/lightdb/util/Nowish.scala

@@ -0,0 +1,20 @@
+package lightdb.util
+
+import java.util.concurrent.atomic.AtomicLong
+
+/**
+ * Always returns an incremented timestamp. If called multiple times within the same millisecond, the returned value will
+ * be incremented to always be unique.
+ */
+object Nowish {
+  private val lastTime = new AtomicLong(-1L)
+
+  def apply(): Long = lastTime.updateAndGet(last => {
+    val now = System.currentTimeMillis()
+    if (now > last) {
+      now
+    } else {
+      last + 1
+    }
+  })
+}