JAVA-374 - Logging of entry to and exit from calls to server

Adding support for logging the calls made to Mongo DB along with time taken. The message log consist of following part. The logs can be enabled by set the LogLevel for 'com.mongodb.TRACE' category

```
Request: Id: <sequence number> (<time taken in millis> ms) <operation name>, [<collection name>]
```
For example below are logs obtained while executing a testcase which consisted of two inserts

```
FINEST: save:  com_mongodb_unittest_QueryLogTest.test { "key1" : "val1"}
FINEST: Request : Id: 1 (5 ms) OP_QUERY, { "isMaster" : 1}
FINEST: Request : Id: 2 (0 ms) OP_INSERT, [test]
FINEST: save:  com_mongodb_unittest_QueryLogTest.test { "key2" : "val2"}
FINEST: Request : Id: 3 (0 ms) OP_INSERT, [test]
```