Logger add modules reader

Currently, the logger is able to write some data from the chemistry and star formation modules, but not read them.

In this merge request, I am implementing the reading part. To do so, I had to change the way we deal with the fields and I implemented a new structure called field_information that contains the indices of the field (and its derivative) in the module and global arrays.

I have also tried to reduce a bit the copy/paste in the main code by using some preprocessing macro.

By the way, SPHENIX is not working anymore (I will fix it in a next merge request) as the number of masks is now too large (I just need to merge together some fields). My next steps are: finish !1256 (merged), merge everything and then change the name of the logger into Continuous Simulation Data Stream (I will use csds in the code).

logger/chemistry/GEAR/logger_chemistry.c

+/*******************************************************************************
+ * This file is part of SWIFT.
+ * Copyright (c) 2020 Loic Hausammann (loic.hausammann@epfl.ch)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ ******************************************************************************/
+
+/* Include this object's header */
+#include "logger_chemistry.h"
+
+/* Local headers  */
+#include "logger_tools.h"
+
+/* Hydro part */
+const int chemistry_logger_field_size_part[chemistry_logger_field_part_count] =
+    {
+        member_size(struct part, chemistry_data.smoothed_metal_mass_fraction) +
+            member_size(struct part, chemistry_data.metal_mass),
+};
+
+int chemistry_logger_local_to_global_part[chemistry_logger_field_part_count];
+
+/* Stellar part */
+const int
+    chemistry_logger_field_size_spart[chemistry_logger_field_spart_count] = {
+        member_size(struct spart, chemistry_data.metal_mass_fraction),
+};
+
+int chemistry_logger_local_to_global_spart[chemistry_logger_field_spart_count];