Feature/documentation topic (#822)

- Implement documentation topic that can be used to query documentation using the network API.
- Implement a way to pass arguments to lua scripts using json (rather than formatting entire lua string clientside)
- Implement ability to attach callback to lua script executions
- Implement abillity to transport return values from lua scripts back to network API clients.
- Do not initialize server interface on slave nodes.
- Implement Dictionary -> json converter using nlohmann json library

src/util/syncbuffer.cpp

@@ -84,20 +84,4 @@ void SyncBuffer::reset() {
     _decodeOffset = 0;
 }
 
-//void SyncBuffer::write() {
-//    _dataStream.resize(_encodeOffset);
-//    _synchronizationBuffer->setVal(_dataStream);
-//    sgct::SharedData::instance()->writeVector(_synchronizationBuffer.get());
-//    _dataStream.resize(_n);
-//    _encodeOffset = 0;
-//    _decodeOffset = 0;
-//}
-//
-//void SyncBuffer::read() {
-//    sgct::SharedData::instance()->readVector(_synchronizationBuffer.get());
-//    _dataStream = _synchronizationBuffer->getVal();
-//    _encodeOffset = 0;
-//    _decodeOffset = 0;
-//}
-
 } // namespace openspace