Added parsing of exptime and period from master files (#256)

- New aare:to_string/string_to similar to what we have in
slsDetectorPackage
- Added members period and exptime to RawMasterFile
- Parsing exposure time and period for json and raw master file formats
- Parsing of RawMasterFile from string stream to enable test without
files

Comments:

- to_string is at the moment not a public header. Can make it later if
needed. This gives us full freedom with the API
- FileConfig should probably be deprecated need to look into it.
Meanwhile removed python bindings and string conv

python/src/raw_master_file.hpp

@@ -85,5 +85,21 @@ void define_raw_master_file_bindings(py::module &m) {
         .def_property_readonly("quad", &RawMasterFile::quad)
         .def_property_readonly("scan_parameters",
                                &RawMasterFile::scan_parameters)
-        .def_property_readonly("roi", &RawMasterFile::roi);
+        .def_property_readonly("roi", &RawMasterFile::roi)
+        .def_property_readonly(
+            "exptime",
+            [](RawMasterFile &self) -> std::optional<double> {
+                if (self.exptime()) {
+                    double seconds =
+                        std::chrono::duration<double>(*self.exptime()).count();
+                    return seconds;
+                } else {
+                    return std::nullopt;
+                }
+            })
+        .def_property_readonly("period", [](RawMasterFile &self) {
+            double seconds =
+                std::chrono::duration<double>(self.period()).count();
+            return seconds;
+        });
 }