Add missiog module dependencies of refactored file API.

Jira issue: WP-601

Add dbox and express dependencies.
Rework createFile() to support systems where exclusive mode doesn't work.

Jira issue: WP-902

This change is primarily for Android that doesn't yet support the new
exclusive-mode flags but other platforms are also potentially problematic.
Merge pull request #538 from paddybyers/living_labs_fileexcl

Living labs fileexcl