New command line LedgerTool. (RIPD-243)

* Retrieve and process summary or full ledgers.
* Search using arbitrary criteria (any Python function).
* Search using arbitrary formats (any Python function).
* Caches ledgers as .gz files to avoid repeated server requests.
* Handles ledger numbers, ranges, and special names like validated or closed.

bin/ripple/util/test_Range.py

@@ -0,0 +1,28 @@
+from __future__ import absolute_import, division, print_function, unicode_literals
+
+from ripple.util import Range
+
+from unittest import TestCase
+
+class test_Range(TestCase):
+    def round_trip(self, s, *items):
+        self.assertEquals(Range.from_string(s), set(items))
+        self.assertEquals(Range.to_string(items), s)
+
+    def test_complete(self):
+        self.round_trip('10,19', 10, 19)
+        self.round_trip('10', 10)
+        self.round_trip('10-12', 10, 11, 12)
+        self.round_trip('10,19,42-45', 10, 19, 42, 43, 44, 45)
+
+    def test_names(self):
+        self.assertEquals(
+            Range.from_string('first,last,current', first=1, last=3, current=5),
+            set([1, 3, 5]))
+
+    def test_is_range(self):
+        self.assertTrue(Range.is_range(''))
+        self.assertTrue(Range.is_range('10'))
+        self.assertTrue(Range.is_range('10,12'))
+        self.assertFalse(Range.is_range('10,12,fred'))
+        self.assertTrue(Range.is_range('10,12,fred', 'fred'))