Added DiracDelta

[fverdugo]

Fixes issue #408

[stevengj]

How do you specify the amplitude? Can you do e.g. 3 * DiracDelta(...) or f * DiracDelta (where f(x) is a function of position)?

[stevengj]

What do you do if you have piecewise-constant test functions, since then you have a discontinuity right where the delta function is? I guess you could use the average of the two sides…

[codecov-io]

Codecov Report

Merging #485 (5a85738) into master (3b7fc18) will increase coverage by 0.11%.
The diff coverage is 85.29%.

@@            Coverage Diff             @@
##           master     #485      +/-   ##
==========================================
+ Coverage   85.69%   85.80%   +0.11%     
==========================================
  Files         143      144       +1     
  Lines       10884    10907      +23     
==========================================
+ Hits         9327     9359      +32     
+ Misses       1557     1548       -9     

Impacted Files	Coverage Δ
src/CellData/CellData.jl	100.00% <ø> (ø)
src/Exports.jl	5.88% <ø> (ø)
src/CellData/DiracDeltas.jl	81.48% <81.48%> (ø)
src/Geometry/BoundaryTriangulations.jl	94.50% <100.00%> (ø)
src/TensorValues/Operations.jl	89.43% <100.00%> (+2.37%)	⬆️
src/Geometry/FaceLabelings.jl	77.39% <0.00%> (+1.20%)	⬆️
src/TensorValues/TensorValueTypes.jl	78.57% <0.00%> (+1.42%)	⬆️
src/Integration/TensorProductQuadratures.jl	95.34% <0.00%> (+8.98%)	⬆️

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