All-Plot - Add "Slope" and "Alt/Slope" curves

... add "Slope" curve based on Slope Data in Ride Files (with separate new color)
... add "Alt/Slope" curve based on "Altitude" data series
... sections on "Alt/Slope" have 3 options -  1min/100 m OR 5min/500 m OR 10min/1000 m
... color / slope assignments are defined in AllPlotSlopeCurve (to look it up)
... if a plotted section is wide enough the slope % (distance) / VAM (time) value is shown above (but only if there is enough room for a text above the segment/section)

Sample Screenshot:

![slope1](https://cloud.githubusercontent.com/assets/7491731/4456888/d7068dc2-488f-11e4-91e7-a24b7bdc5d96.png)
![slope2](https://cloud.githubusercontent.com/assets/7491731/4456889/d7070dba-488f-11e4-88fc-37973fb6a986.png)