Fixing DFS implementation of DAG validation to be much faster
Adding in additional tests to ensure the run order of expanded tasks is preserved
Adding additional compile-time checks, resolving issues that came up as a result
- Adding support for SlurmTaskExecutor in `daggyd` if DAGGY_ENABLE_SLURM is defined.
- Renaming some test cases
- Enabling compile-time slurm support
- Adding slurm documentation
- Changing how DAG is represented, both in code and how DAGs are defined
in JSON.
- Removing std::vector<Task> representation in favour of a map that will
enforce unique task names
- Task names now have a name (generated), and a definedName.
- Adding support to loggers to add tasks after a DAGRun has been
initialized.
