Home housekeeping and minor refactoring cleanup.

Changed README from AsciiDoc (.asciidoc) to traditional markdown (.md).
Plan to use AsciiDoc for more in depth documentation guides, but stick
to more general markdown for README files.

Renamed 'ScalaFileImporter' to (the more appropriate) 'DefaultFileImporter'.

Renamed 'FileImporter' and 'DirectoryImporter' to 'FileBundleImporter' and
'DirectoryBundleImporter' respectively.

Fixed indefinite directory recursion.

Shortened 'Bundle' property "bundleSymbolicName" to "bsn" to make
queries easier on the fingers.