Added fitting, fixed roi etc (#129)

Co-authored-by: Patrick <patrick.sieberer@psi.ch>
Co-authored-by: JulianHeymes <julian.heymes@psi.ch>

include/aare/utils/task.hpp

@@ -0,0 +1,8 @@
+
+#include <utility>
+#include <vector>
+
+namespace aare {
+std::vector<std::pair<int, int>> split_task(int first, int last, int n_threads);
+
+} // namespace aare