EHTMLEditorView - Optimize the put_body_in_citation function

Use DOM operations instead of manipulating with strings. Before this
change the HTML test message spent there 160 ms afterwards 21 ms.
EHTMLEditorView - Decode the HTML encoded string only when ampersand is presented
EHTMLEditorView - After wrapping use the faster approach for quoting the content

Replying on the selection from preview (30 lines of selection)
    - speedup from ~4 ms to ~1 ms
Switching from HTML to Plain Text mode in already converted message with citations
    - speedup from ~85 ms to ~30 ms
Switching from HTML to Plain Text mode and confirming that we want to lose the formatting
    - speedup from ~51 ms to ~18 ms
EHTMLEditorView - Use BR element instead of zero width space character and selection markers instead of caret position