EEditor: Avoid crash when no proxies are returned
EEditorWidget: Repair GMail blockquotes when editting message as new
EEditorWidget: Make Paste Quotation working in plain text mode

Also correctly restore caret position
EEditorActions: Don't try to continue if given object is not EEditor
EEditorSpellCheckDialog: Get DOM Document from correct widget
EEditorSelection: Replace DOM Selection direction

Replace it with direction based on the language at the selection point.
EEditorWidget: Remove inline images when changing the composer mode to plain
EEditorWidget: Convert text correctly from HTML to plain when editting message as new

Also with this change the behavior of citations is unified as it will
always be unwrapped (in plain text mode) and formatted as prefomatted.
EEditorWidget: Return wrapped body in e_editor_widget_quote_plain_text
EEditorWidget: Return NULL when the citation is already quoted
EEditorWidget: Remove unused code
Rename -x-evolution-signature to -x-evo-signature
EMsgComposer: Remove unused code