add type information to RenderedTrees (Fixes #106)

use a single case class for RenderedTrees (but with alias constructors Terminal and NonTerminal)

nodeTypes for Workflow trees

nodeTypes for LogicalPlan (and annotated forms)

nodeType for None

nodeTypes for AST annotations

handle the umpteen AST node types in RenderTree instance
workaround for Travis' download issues
Merge pull request #145 from mossprescott/106-rendered-tree-type-info

add type information to RenderedTrees (Fixes #106)
tests for API with stubbed backend (Fixes #143)
fix handling of missing paths; normalize paths in backend configuration
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