Created Dockerfile (Dockerfile.linux-image.build) and docker-compose for generating
a local docker image with build enviroment from the pulled branch.
Initial testing and and recompiles can be made, but it not setup for git pushes.
WIP - Addon to this would be to setup git commits and changes for active development.
Fixed Yaml (xml_config.yaml) Load issues.
config.hpp hidden_input_field_char was an unsigned char which seems to be an
issue in the latest yaml-cpp v7.0. Converted the variable to an std::string.
Added a missed "use_address" configuration option.