dropbox: Add new package with Dropbox's endpoint

[nkprince007]

Change-Id: I3d3cd624b7878465fa2b11982e076d633dfe6381

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Message from Gerrit User 12446:

Uploaded patch set 2: Commit message was updated.

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Message from Gerrit User 27740:

Patch Set 2:

Reference: https://www.dropbox.com/developers/documentation/http/documentation

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Message from Gerrit User 5065:

Patch Set 2: Code-Review-2

Sorry, we're no longer accepting new endpoint packages per #325

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