Split up styling process in tree manipulation & writing output to allow advanced tree manipulation scenarios.  Added grid child ordering to styling process.
Added Canvas children ordering
Added styler options for Grid/Canvas children reorder
Take user options for panel children order into account
Ensure correct attribute handling for nested elements
Ensure package Execute uses new formatting process
Unit tests for grid/canvas children reorder
Use parallel processing when multiple files are affected
Merge pull request #7 from KevinDockx/master

Grid/Canvas reorder, parallel processing of multiple files, unit tests, styling process splitup