Adding support for execution on slurm grids

- Adding support for SlurmTaskExecutor in `daggyd` if DAGGY_ENABLE_SLURM is defined.
- Renaming some test cases
- Enabling compile-time slurm support
- Adding slurm documentation

utils/daggyd/daggyd.cpp

@@ -10,7 +10,13 @@
 #include <daggy/Server.hpp>
 
 // Add executors here
+#ifdef DAGGY_ENABLE_SLURM
+
+#include <daggy/executors/task/SlurmTaskExecutor.hpp>
+
+#else
 #include <daggy/executors/task/ForkingTaskExecutor.hpp>
+#endif
 
 // Add loggers here
 #include <daggy/loggers/dag_run/OStreamLogger.hpp>
@@ -178,7 +184,11 @@ int main(int argc, char **argv) {
         logger = std::make_unique<daggy::loggers::dag_run::OStreamLogger>(logFH);
     }
 
+#ifdef DAGGY_ENABLE_SLURM
+    daggy::executors::task::SlurmTaskExecutor executor(executorThreads);
+#else
     daggy::executors::task::ForkingTaskExecutor executor(executorThreads);
+#endif
     Pistache::Address listenSpec(listenIP, listenPort);
 
     daggy::Server server(listenSpec, *logger, executor, dagThreads);