Fix isUpToDate for sub packages
Merge pull request #336 from sinkuu/fix_subpkg_isuptodate

Fix isUpToDate for sub-packages
Use "dub.json" instead of "package.json" in documentation
Use "dub.json" instead of "package.json" when reading from zip archives
Renamed all "package.json" files to "dub.json"
Merge pull request #337 from jrtc27/dub-json

Use new dub.json file everywhere
Converted line endings from CRLF to LF
Removed trailing whitespace
Merge pull request #338 from jrtc27/whitespace

Cleaned up whitespace
Use tabs in all JSON and D files
Ensure all files end with a newline
Removed extra spaces between words
Merge pull request #339 from jrtc27/whitespace

Further whitespace cleanup
Recognize the "systemDependencies" field.
Output all possible source/import files for "dub describe". Fixes #185.

Files that are not used for the current configuration or platform are output with an "unused" prefix (e.g. "unusedSource").
Update change log.
Avoid redundant loading of packages and remove PackageManager.getTemporaryPackage.
Print a proper error message for unknown dependency versions of the root package.
Update GitHub links in README.md
Avoid probing all versions of the root package when resolving its own sub packages.

This avoids downloading all versions of the root package whenever it contains references to sub packages of itself. See #334.