Setting DIR_X/Y/Z/C automatically #168
Description
When getting an empty field from the allocator we are required to pass a dir (DIR_X|DIR_Y|DIR_Z|DIR_C) so that the 3D shape is set correctly.
f => allocator%get_block(DIR_X)
In most cases specifiying a dir is redundant, because most common operations we have, tds_solve and reorder, can both figure out the direction of the output field. This is similar to data_loc as discussed in #98 and then implemented in #125. I'll investigate the impact of this potential change in the codebase and work out a draft. If we can fully automate setting dir as we did with data_loc it should simplify the implementation of high-level operations and help new users.