A first pass at documenting build plugins

Documentation for the CompileStep is only in the source right now
Allow CompileStep#addAsset to accept Strings for content
Fix bug where backcompat for registerBuildPlugin didn't work
Document packageName
Document Buffer or String argument in addAsset
Add newlines between CompileStep methods
Consistently name path variables
Fix link
Add fullInputPath to public API
Document arch

Fix documentation typo
Rename appendDocument to addHtml
Rename back pathForSourceMap
Fix a big typo
Fix incorrect packageName docs
Pass through 'bare' option to compiled js source files
Add link to Wiki, add warning that comments aren't used
Fix typo
Update meteor
Support asymptotic progress bar for constraint solver

Until we either can estimate progress or have a spinner...
Change the 'easy' instances of rawLog to use Console

Rationalizing logging is definitely a TODO