Adding range based pruning to bloom index

- keys compared lexicographically using String::compareTo
 - Range metadata additionally written into parquet file footers
 - Trim fat & few optimizations to speed up indexing
 - Add param to control whether input shall be cached, to speed up lookup
 - Add param to turn on/off range pruning
 - Auto compute of parallelism now simply factors in amount of comparisons done
 - More accurate parallelism computation when range pruning is on
 - tests added & hardened, docs updated

hoodie-client/src/test/java/com/uber/hoodie/table/TestCopyOnWriteTable.java

@@ -69,8 +69,7 @@ public class TestCopyOnWriteTable {
     public void init() throws Exception {
 
         // Initialize a local spark env
-        SparkConf sparkConf = new SparkConf().setAppName("TestCopyOnWriteTable").setMaster("local[4]");
-        jsc = new JavaSparkContext(sparkConf);
+        jsc = new JavaSparkContext(HoodieClientTestUtils.getSparkConfForTest("TestCopyOnWriteTable"));
 
         // Create a temp folder as the base path
         TemporaryFolder folder = new TemporaryFolder();