Feature request: tweaks to "Special Characters" dialog

This issue requests three minor changes to the "Insert | Special Characters"
dialog, all intended to improve usability. Should these requests be
programatically distinct, feel free to split the issue.

1. At present, when a character is selected, the dialog shows a zoomed view of
the character, and its Unicode value. The request is for the character's Unicode
name to be shown as well (eg "LATIN SMALL S WITH DOT BELOW"), as per Unicode's
scheme (see http://unicode.org/Public/UCA/5.2.0/allkeys.txt - a more recent
version may exist).
The enchancement removes confusion between visually similar but semantically
very different characters, which can be indistinguishable depending on font
design, hinting, and/or screen resolution. For example, can you tell the
difference between these:  ᾽ ᾿ ’ ʼ  ̓  ̕ ? (if this looks corrupt, your font lacks
some of the characters)

2. At present, the zoomed character view and Unicode value are only shown when a
glyph is actually selected (and thus added to the selection string). The
information would be more usefully displayed before character selection, meaning
on mousing over.

3. At present, the dialog's Delete button clears the entire selection string;
kinder would be for it to clear only the last character added. If implemented,
"Undo" might be a better button label.

Many thanks