Preparing backend to receive data from shards (#337)

* Move backend to backend/core

* Ported shard receiver WIP

* Remove dead code

backend/core/src/util.rs

@@ -0,0 +1,31 @@
+mod dense_map;
+mod hash;
+mod location;
+mod mean_list;
+mod num_stats;
+
+pub use dense_map::DenseMap;
+pub use hash::Hash;
+pub use location::{LocateRequest, Locator, LocatorFactory};
+pub use mean_list::MeanList;
+pub use num_stats::NumStats;
+
+pub fn fnv<D: AsRef<[u8]>>(data: D) -> u64 {
+    use fnv::FnvHasher;
+    use std::hash::Hasher;
+
+    let mut hasher = FnvHasher::default();
+
+    hasher.write(data.as_ref());
+    hasher.finish()
+}
+
+/// Returns current unix time in ms (compatible with JS Date.now())
+pub fn now() -> u64 {
+    use std::time::SystemTime;
+
+    SystemTime::now()
+        .duration_since(SystemTime::UNIX_EPOCH)
+        .expect("System time must be configured to be post Unix Epoch start; qed")
+        .as_millis() as u64
+}