Function to convert strings to UTF with no BOM

Remove BOM, test broken and converted string lengths, encode if needed
and also show a message if required.
Convert content to UTF8 no BOM

Detect bad chars and BOMs in loaded content and convert plus show
message to inform user
Affects: Loaded files, remote loaded files, replacing text in files,
saving files
Test against converted UTF8 no BOM content

Convert content to UTF8 with no BOM before testing matches against it