Sorted Vector & binary search functionality.

Bug: 16659276
Tested: on Linux & Windows.

Change-Id: Ie7a73810345fad4cf0a3ad03dfaa5464e3ed5ac8

docs/source/Schemas.md

@@ -275,6 +275,9 @@ Current understood attributes:
     (which must be a vector of ubyte) contains flatbuffer data, for which the
     root type is given by `table_name`. The generated code will then produce
     a convenient accessor for the nested FlatBuffer.
+-   `key` (on a field): this field is meant to be used as a key when sorting
+    a vector of the type of table it sits in. Can be used for in-place
+    binary search.
 
 ## JSON Parsing