Fix MAGN-3037 Port XyzAverage
Merge branch 'master' of github.com:DynamoDS/Dynamo
Merge branch 'master' of https://github.com/Randy-Ma/Dynamo
Merge branch 'master' of github.com:DynamoDS/Dynamo
Added a test case for XyzAverage migration
Minor cleanup for readability
Merge branch 'XyzAverageTest' of https://github.com/ellensi/Dynamo
Merge pull request #1531 from ke-yu/code_cleanup

Minor cleanup for readability
Merge pull request #1520 from Randy-Ma/master

Fix MAGN-3037 Port XyzAverage
updated documentation for CoreNodes/math
Second pass through CoreNodes documentation: removed redundant search tags
Documentation for CoreNodes/string
Forced ReExec refactorings

Update name of forced re-execution property, update the property  in the selection nodes, introduce added element watcher
reorganized startup logic
fixed uuid loading for selection nodes
Minimal multi-thread trace test
Move the test to outside the thread
Documentation for Python nodes