Add DataflowGraph and fix part of substitutions

[lockshaw]

Description of changes:

Also adds proj doxygen support.

Related Issues:

Linked Issues:

• Issue #

Issues closed by this PR:

• Closes proj support for local doxygen rendering #1341

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This change is 

[wmdi]

Reviewed 304 of 493 files at r1, 263 of 445 files at r2, 170 of 181 files at r3, 16 of 16 files at r4, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @lockshaw and @Marsella8)

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lib/substitutions/include/substitutions/substitution.h line 12 at r4 (raw file):

bool is_valid_substitution(Substitution const &);

SubParallelComputationGraph

Could you also add simple descriptions for the main functions? I feel like each time I need to recall their definition for a while.

[lockshaw]

Reviewable status: 750 of 760 files reviewed, 1 unresolved discussion (waiting on @Marsella8, @reyna-abhyankar, and @wmdi)

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lib/substitutions/include/substitutions/substitution.h line 12 at r4 (raw file):

Previously, wmdi (Mengdi Wu) wrote…

Could you also add simple descriptions for the main functions? I feel like each time I need to recall their definition for a while.

Added!

[wmdi]

Reviewed 10 of 10 files at r5, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @Marsella8 and @reyna-abhyankar)

[wmdi]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @Marsella8 and @reyna-abhyankar)