new function to convert get_xml_files_param_df long format output to wide format

[plecharpent]

⚠️ Take care of plant index and soil layer index in initialisation data and take also into account plant files for cultivar ids!
The wide format generated by get_xml_files_param_df seems ok for plant files but not the wide format.

For the moment the long format table contains param names (col = param) attached to crop i.e. lai0_Crop1, lai0_Crop2 and also param names with soil layer id and plant id i.e. densinitial_1_Crop1, densinitial_2_Crop1,...

name type param id value
... ... ... ... ...
23 mais_ini.xml initialisations lai0_Crop1 NA 0.0
24 mais_ini.xml initialisations lai0_Crop2 NA
... ... ... ... ...
45 mais_ini.xml initialisations densinitial_1_Crop1 NA 0.0
46 mais_ini.xml initialisations densinitial_2_Crop1 NA 0.0
47 mais_ini.xml initialisations densinitial_3_Crop1 NA 0.0
48 mais_ini.xml initialisations densinitial_4_Crop1 NA 0.0
49 mais_ini.xml initialisations densinitial_5_Crop1 NA 0.0

So, soil id must be set into id column of the table and a new crop id col should be added as follows

name type param soilid cropid value
... ... ... ... ... ...
23 mais_ini.xml initialisations lai0_Crop1 NA 1 0.0
24 mais_ini.xml initialisations lai0_Crop2 NA 2
... ... ... ... ... ...
45 mais_ini.xml initialisations densinitial_1_Crop1 1 1 0.0
46 mais_ini.xml initialisations densinitial_2_Crop1 2 1 0.0
...

The actual function producing the long table from xml files (get_xml_files_param_df) has to be modified to take it into account.