Add after-save-hook to correct buffer
For symlinks, use modification time of target

Call file-truename before file-attributes.
When opening files, move point to first match

Includes a new function, `deft-filter-regexp-as-regexp' that
converts the filter string to a proper regular expression,
depending on which search mode is active.

When opening a file, search forward to the beginning of the
first match of the filter string.
Safely handle empty title or contents