SetSampleMaterial improvements

[peterfpeterson]

This ticket is blocked by :

• TRAC7285

Chatted with Christina a Xiaoping today and many things were pointed out concerning SetSampleMaterial and some related algorithms.

1. SetSampleMaterial should print units on the values being set
2. SetSampleMaterial should work on a peaks workspace
3. SetSampleMaterial should get the unit cell volume from the lattice if it is already attached to the workspace
4. Clarify language concerning units of SampleNumberDensity
5. Modify gui for SetSampleMaterial and help so it is clearer which parameters override which
6. The logging of values should not abbreviate "Cross Section" as "X Section" as some people interpret it to mean the values for x-rays
7. The scattering cross section does not appear to generate the correct value for "K1-C6-O6". Verify the value and fix the bug.
8. Setting the chemical formula from C to C60 should do the same thing, currently C60 doesn't work.

[peterfpeterson]

This issue was originally trac ticket 7279