System is fast enough that sometimes SystemClock.currentTimeMillis() is duplicated
when used to make a unique filename.

Change-Id: I9454fbb5e10265d36b8e17cba183a1591d52cc7b

Previously used a monotonically increasing int.  Now uses uuid and nanoseconds.

squashed in:
    [FileEncap11] Read preference from ResearchSettings
    Change-Id: Ic779e0a69db6b16e92c6f4b63dbe7b7add566ab6

    [FileEncap12] Simplify directory cleanup invocation
    Change-Id: I688047409c0343d32b11447fb625dfb726c731ec

    [FileEncap14] Change log filename syntax
    Change-Id: I9243b20b2eb392f81ab8c5c3d19315211240e0bc

Change-Id: I5c9d70e0cb7b0965158e17dd71dfab796bd9a440