Get dependencies with CMake

Created by: matthew-d-jones

I have managed to build this on my system (Ubuntu 16.04). As I needed to install some of the dependencies I altered the cmake code to download these for me. This has the advantages of there being a version specified in the repository and the dependencies only being in the build directory rather than polluting the whole system.

So far I have tried running the tests and dummy targets. dummy fails with this output:

fake_recv
Streamer.cxx:122 [3]:  Failed to consume :	Local: Timed out
Streamer.cxx:122 [3]:  Failed to consume :	Local: Timed out
Streamer.cxx:122 [3]:  Failed to consume :	Local: Timed out
Streamer.cxx:122 [3]:  Failed to consume :	Local: Timed out

tests fails at:

[----------] 3 tests from T_CommandHandler
[ RUN      ] T_CommandHandler.new_03
tests: /home/jonmd/git/kafka-to-nexus/cmake-build-debug/rapidJSON-src/include/rapidjson/document.h:1154: rapidjson::GenericValue<Encoding, Allocator>::MemberIterator rapidjson::GenericValue<Encoding, Allocator>::FindMember(const rapidjson::GenericValue<Encoding, SourceAllocator>&) [with SourceAllocator = rapidjson::MemoryPoolAllocator<>; Encoding = rapidjson::UTF8<>; Allocator = rapidjson::MemoryPoolAllocator<>; rapidjson::GenericValue<Encoding, Allocator>::MemberIterator = rapidjson::GenericMemberIterator<false, rapidjson::UTF8<>, rapidjson::MemoryPoolAllocator<> >]: Assertion `IsObject()' failed.

Do you see the same behaviour or do I have something misconfigured? I've included rapidjson v1.1.0, are you perhaps using a different version?

I realise dependency management is a topic under discussion and you may not want to merge this branch, but the main objective of this PR is to start discussing this codebase with you.