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.

Signed-off-by: Nisarg Jhaveri <nisargjhaveri@gmail.com>
Fixed tests for regex Find and replace

Signed-off-by: Nisarg Jhaveri <nisargjhaveri@gmail.com>
Removed trailing space

Signed-off-by: Nisarg Jhaveri <nisarg.jhaveri@students.iiit.ac.in>