AppNexus parsing/handing bid request works; new version of realtime-bidding.proto
parsing ok. (both mobile and single tag BR)
answers: no_bid to requests sent by AppNexus; need to beef up the response -> done
adding creative compatibility check
adding support for providerConfig. support for membership and excluded attributes;
fixed test
Reworked the bid request synthetizer.
Merge branch 'APPNEXUS' of https://github.com/jsulmont/rtbkit into jsulmont-APPNEXUS
Virtual default destructor to avoid compiler warning

The warning was

```
./rtbkit/common/testing/bid_request_synth.cc: In destructor ‘RTBKIT::Synth::NodeObject::~NodeObject()’:
./rtbkit/common/testing/bid_request_synth.cc:267:26: error: deleting object of abstract class type ‘RTBKIT::Synth::Node’ which has non-virtual destructor will cause undefined behaviour [-Werror=delete-non-virtual-dtor]
             delete field.second;
                          ^
cc1plus: all warnings being treated as errors
```
Merge pull request #108 from dohse/virtual-constructor-warning

Virtual default destructor to avoid compiler warning
Fixed the bid request synth build error on gcc 4.6
Added internal support for contexts in the bid request synth.
Added full support for cutoff and generated keys in the bid request synth.
Can now set the generator seed.
made default tmax 30ms and network default round trip time 20ms to make sure that bid requests aren't rejected if tmax isn't specified in the bidrequest
Merge pull request #109 from rtbkit/latency-exp

made default tmax 30ms and network default round trip time 20ms to make ...
Added a cpu intensive realtime polling option for the exchange connectors.
Fix race condition in the router
Submodule update for jml and soa