Add option to save snippet information in HTML

[delphidabbler]

The facility to save snippet information to file was added (in develop at merge commit 1b54e43).

A comment on issue #140 that proposed this feature noted:

For ease of implementation it may be best to stick to RTF output if and when this is first implemented. If that implementation makes it to release then a new issue could be added to add the save as HTML option.

So here's the proposed issue to generate the information in HTML as an option.

It would be best to replace the existing save dialogue box with a customised version that lets the user choose between the two possible file types.

[delphidabbler]

This has been made a sub-issue of #140.

[delphidabbler]

No longer a sub-issue of #140.