feature 857: Regex search and replace

- Implemented basic regex search and replace for tables.
- Added a checkbox to use regex in 'Find and Replace' view.
- Fixed some tests for this feature

Signed-off-by: Nisarg Jhaveri <nisarg.jhaveri@students.iiit.ac.in>
Merge pull request #1334 from nisargjhaveri/feature_857

feature 857: Regex search and replace