Update searchreplacedb2.php

Added dry-run option as check-box. Default state is checked.
Check for state of check-box and if set, bypass actual SQL update calls.
Adjusted wording of report for dry-run use case. Also add reminder that no updates were made by adding feedback into error queue (which shows up in red box above report).
Update README.md

Added dry-run step for web version.
Merge pull request #27 from bsy-web/master

Dry-run option added to step 4 page. Report language updated for dry-run case. Minor changes to wording of submit button and user feedback text.