v0.19.0

DistributedFactorGraphs v0.19.0

Diff since v0.18.10

Closed issues:

• Variables should be top level JSON serialization only (#867)
• Deprecate LightDFG (#935)

Merged pull requests:

• Preparation for v0.19 (#918) (@GearsAD)
• simpler packVariable (API depr) (#926) (@dehann)
• serialize DFGVariable top level JSON only (#933) (@dehann)
• common dispatch for solveGraph! and Parametric (#934) (@dehann)
• Remove LightDFG and deprecate with error (#936) (@Affie)
• add transcodeType util for super unmarshal (#937) (@dehann)
• rm depr pre-v0.19 (#940) (@dehann)