minor doc fixes

[redman-a]

Various sporadic documentation changes

• resfields: fixes closing code block
• userguide_pepper: removed discussion of legacy Exp.Temperature for non-equilibrium populations
• rotview: corrected file name and updated image
• sphgrid: added discussion of tri output and changed input to GridSymmetry for consistency with Opt.GridSymmetry
• hams: tried to make input syntax consistent across functions
• installation: changed minimum MATLAB version for consistency with current progress in #160

[stestoll]

Looks great! Thanks for all these fixes!