Resolve "Add Tri6 element"

Closes #22

See merge request mechanics-and-materials/ae108!22

Resolve "Add Tri3 element"

Closes #20

See merge request mechanics-and-materials/ae108!20

Resolve "Output example writes to file opened with "read" access"

Closes #21

See merge request mechanics-and-materials/ae108!21

Resolve "Add AssembleConsistentMassMatrixPlugin"

Closes #19

See merge request mechanics-and-materials/ae108!19

Resolve "Add `Viewer::fromBinaryFilePath`"

Closes #18

See merge request mechanics-and-materials/ae108!18

Resolve "Add `Mesh::fromCanonicalOrder`"

Closes #17

See merge request mechanics-and-materials/ae108!17

Resolve "Add script to compare text files that contain printed vectors"

Closes #16

See merge request mechanics-and-materials/ae108!16

Resolve "Use PETSc's `DM` to store `SF`s"

Closes #15

See merge request mechanics-and-materials/ae108!15

Resolve "Read Vectors from HDF5 files"

Closes #14

See merge request mechanics-and-materials/ae108!14