Refs #8962 Fixes to loader

The loader had a problem where large groups of commas at the start of the row would cause the loader to become confused and skip a cell. Fixed so that it now looks if it was the first column or not, rather than looking at the place of the last found comma.

The stitch ID has been fixed to be an int to help the save algorithm
Refs #8962 Written unit test for Loader

Test includes cases for unquoted data, quoted data, incorrect columns and blank files