conf2: implemented all list operations in the interpreter

conf2: implemented all list operations in the interpreter

- added operations OP_EDIT, OP_AFTER, OP_BEFORE, and flags OP_1ST, OP_2ND
  denoting the phase (forming a search query vs. filling in the data)
- add_to_list() extended to support all list operations
- definition of stack moved closer to the interpreter, because many
  functions don't need it
- implemented find_list_node(), opening_brace (former increase_stack), and
  closing_brace() that fully support all operations
- the top of interpret_line() rewritten too