Purkinje solver changes

[bergolho]

Hello Sachetto,

These are a few changes that I did to the solver during December and January:

• Merging Sachetto's changes from November and December
• Improvements in the 'link_purkinje_to_tissue' functions.
  • Coupled tissue cells must be linked to only one Purkinje cell. (uniqueness)
• New script to tune the PMJ delay using a Purkinje cable couple to a cuboid (tunePMJ)
• New script to compress local and private files
• Remove unused result files in the 'scripts/error_calculator' folder
• Fix a segmentation fault error when a tissue cell is not activated by the Purkinje and we want to write its LAT
• Add a function to print Purkinje terminal information
• Add a new matrix assembly function when using a fast endocardial layer. (needs improvements)