add CTelnetView::ConvStr2SiteEncoding() for convert string and get last line word count

add the API for general inherit usage, convert string encoding and calculate last line word count
the word cound should skip the control char(wrap by '\x1b' and 'm')
refine CEditorView process logic about past text from clipboard

refine CEditorView::DoPasteFromClipboard() to use ConvStr2SiteEncoding()
simplify the logic about convert encoding and calculate the lines count and words count of last line