v1.30 - Material Densities

Added a set of common material densities (all measured in kg/m³) to the page of scientific constants. These densities can be useful when (for example) estimating the mass of a part.

For example, imagine a 400 mm length of 60 mm diameter aluminium round bar. The area of a circle is πr², so the volume of the cylinder is πr²l, so the calculator can be used to calculate the volume as approximately 1,130,973 mm³. The conversion button "m³←" converts this to 0.001131 m³ and multiplying this by the density of aluminium (2700 kg/m³) gives the expected mass of 3.05 kg.

The android version has also been updated; this can be downloaded from https://rpn.cgtk.co.uk/android/latest.html