hyperlink: defined a new named color clHyperLink and used in in TfpgHyperLink

This makes it easier to customise in themes - without needing to override
TfpgCanvas.DrawString()
hyperlink: Removed hard-coded font name, and make it more cross-platform friendly.
Merge branch hyperlink into develop

Small branch that contained some improvements to the TfpgHyperLink widget.