For this upload we expect a single text file, with numeric values, space and line separated. The numeric values in
the uploaded file should hold a matrix of size (n, m). n is the number of sensors, and m is the number of nodes.
When the projection matrix we want to import is a Surface Projection Matrix, m will be the number of vertices in
the target Cortical Surface. When the projection matrix is a region-level one, m will be the number of regions in
the Connectivity. Having headers in the text file is not accepted. An incorrect number of values (lines or rows) in
the Projection Matrix will also raise an exception.