Allow having data somewhere that is not in the position folder

[ElpadoCan]

Description:

To avoid copying data from raw microscopy file to .tiff files, add an option to the data structure module to save a .link file with the location of raw microscopy file. Cell-ACDC should then read image data from the raw file

[ElpadoCan]

Another idea is to have a ini file inside the position folder with the paths of the source data for channels and segmentation files. @Teranis