Detect Byte Order Mark and wrap a rectangle around multiple bytes that encode a certain codepoint

[yetibrain]

Detect the BOM on Text Files and wrap a rectangle around the bytes (as Editor MadEdit is doing it). For utf-8 endoded files, match single-bytes with the correspondig character. Match 2-, 3- as well as 4-byte sequences as well and wrap a rectangle around the bytes of the sequence. Like this, the user can see easily where there is a sequence e. g. an encoded codepoint and at the same time see the codepoints glyph in the right panel. For utf-16 encoded files, wrap surrogate-pairs with a rectangle and show the encoded glyph of the codepoint in the right panel.