As a User, I want to change the output extension when exporting using a TXT template

As a User, I want to change the output extension when exporting using a TXT template.
This feature should be implemented for:

1. Single Export
2. Bulk Export
3. Xporter Reports
4. Scheduled Reports
5. Post Functions (Send Email and Create Document)

Apart from the TXT file format, the file types to add are the following:

1. HTML
2. XML
3. JSON
4. CSV