EEditorWidget: When getting plain text from composer wrap paragraphs in BODY clone

Don't do it in original BODY as we don't want to modify the body structure
for next calls. Before this change when we were sending HTML mail (we
are sending HTML and plain text version at same time) with
long lines the e_editor_widget_get_text_plain was issued before
e_editor_widget_get_text_html so even in HTML mail we sent the wrapped
text instead of unwrapped.
EEditorWidget: Don't wrap paragraphs after conversion from HTML to plain text

GtkHTML based composer is not doing it as well. Also insert
UNICODE_ZERO_WIDTH_SPACE into paragraph above converted text to get
the right initial caret position.
EEditorWidget: Try to remove UNICODE_ZERO_WIDTH_SPACE just when there is 1+ characters
EEditorSelection: Fix list and block format handling in composer
EEditorSelection: Force spellcheck on newly formated blocks
EEditorSelection: Show caret position node and change its color to red

Caret position node should be never visible to user, but when it is visible,
something went wrong.