Refactor directory API to "opening document tree."

Cleans up API so it consistently refers to opening or working with a
subtree of documents.  Also separates isChildDocument() support from
the concept of directory tree selection.

Bug: 15429194
Change-Id: Ice66a751ff4bd0cc4d34c44c5da13a0dc4186dc9
4 files changed
tree: fcbf01db0747cb484915492dec8cec700a6c0159
  1. res/
  2. src/
  3. tests/
  4. Android.mk
  5. AndroidManifest.xml