Add option to replace existing entry

[LauLauThom]

Currently annotating the same image or ROI will result in duplicate entries in the table.
Give the option to replace existing entries.

This means checking some column values to see if they contain the value which is about to be appended.
The branch overwrite-bruteforce-search adds a checkbox "Overwriting existing" and a function to find existing rows provided a folder, image and optional slice and roi identifier.

Problem: when measurement is selected the analyzer automatically adds to the result table
From there possible solutions:

• make the analyzer write to another table with a unique ro, read this row into a dictionary and close the table
• check if Measure: read last row, delete last row, replace existing row
• modify the Analyzer class so that it returns the measurement into a variable (but then not available for current version of ImageJ/Fiji)