Add unitless dispatch for more trig functions

[derikk]

Dispatch on unitless quantities (like 10m/3km) for inverse and hyperbolic trig functions. Fixes #332.

[giordano]

Awesome, thank you so much!

[codecov-io]

Codecov Report

Merging #387 into master will decrease coverage by 2.74%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #387      +/-   ##
==========================================
- Coverage   83.16%   80.41%   -2.75%     
==========================================
  Files          15       15              
  Lines        1283     1195      -88     
==========================================
- Hits         1067      961     -106     
- Misses        216      234      +18     

Impacted Files	Coverage Δ
src/Unitful.jl	100.00% <ø> (ø)
src/quantities.jl	94.08% <ø> (-0.01%)	⬇️
src/complex.jl	83.33% <0.00%> (-16.67%)	⬇️
src/display.jl	87.50% <0.00%> (-6.33%)	⬇️
src/range.jl	77.77% <0.00%> (-6.23%)	⬇️
src/units.jl	82.87% <0.00%> (-3.61%)	⬇️
src/promotion.jl	40.00% <0.00%> (-3.48%)	⬇️
src/logarithm.jl	66.07% <0.00%> (-3.09%)	⬇️
src/conversion.jl	83.87% <0.00%> (-2.70%)	⬇️
src/types.jl	89.36% <0.00%> (-2.64%)	⬇️
... and 5 more

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