Adding support for isGenerator tasks

- 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.

tests/unit_server.cpp

@@ -74,16 +74,12 @@ TEST_CASE("Server Basic Endpoints", "[server_basic]") {
         std::string dagRun = R"({
             "name": "unit_server",
             "taskParameters": { "FILE": [ "A", "B" ] },
-            "tasks": [
-               { "name": "touch",
-                 "command": [ "/usr/bin/touch", "dagrun_{{FILE}}" ]
-               },
-               {
-                 "name": "cat",
-                 "command": [ "/usr/bin/cat", "dagrun_A", "dagrun_B" ],
+            "tasks": {
+               "touch": { "command": [ "/usr/bin/touch", "dagrun_{{FILE}}" ] },
+               "cat": { "command": [ "/usr/bin/cat", "dagrun_A", "dagrun_B" ],
                  "parents": [ "touch" ]
                }
-               ]
+               }
         })";
 
 
@@ -160,7 +156,7 @@ TEST_CASE("Server Basic Endpoints", "[server_basic]") {
         REQUIRE(complete);
 
         std::this_thread::sleep_for(std::chrono::seconds(2));
-        for (const auto &pth : std::vector<fs::path>{"dagrun_A", "dagrun_B"}) {
+        for (const auto &pth: std::vector<fs::path>{"dagrun_A", "dagrun_B"}) {
             REQUIRE(fs::exists(pth));
             fs::remove(pth);
         }