+** make Inset::display() more useful
+
+Extending the DisplayType enum would allow to remove special cases
+from the code.
+
+The enumeration could be like
+: Inline = 0
+: BreakBefore = 1 // break row before this inset
+: BreakAfter = 2 // break row after this inset
+: CanBreakAfter = 4 // optionally break row after this inset
+: AlignLeft = 8
+: AlignRight = 16
+: NoBoundary = 32 // do not allow cursor to go at the end of the row
+: //before display inset
+: Display = BreakBefore|BreakAfter
+
+A display equation would be Display, other could be Display|AlignLeft
+BreakAfter can be used by Newline or separator insets
+CanBreakAfter can be used by the optional hyphen InsetSpecialChar.
+