Make trend cursor readable on busy trends

When adding a trend cursor to the display, the date, time and values can be obscured by the trend title or trend itself. Also, when adding multiple trend cursors that are "too close" the text will overlay each other making it impossible to read. The textbox associated with the cursor should try and default to an open space.

If the cursor is moved around to a more visible part of the trend, it will also change the date/time/values displayed. We need to be able to see the textbox at the time specified which may be under the title or in a busier part of the trend. The simplest way might be to make the background non-transparent. However, that will not solve the problem where they obscure each other. In any of the cases, the textbox should be visible.