Removed some old, unused code
Add set id and path to cell collection

…so cells can get to it
Added cell-id field to set_link cell

Resolves #47
added some nice utility functions to get cells by path or id

unfortunately unneccessary atm.
Implemented 'path' field for cells

Resolves #70
Fixed clicking same cell link multiple times in a row

Resolves #49
Merge branch 'link-fix'