This is mostly a matter of taste, but it matches more closely with the
old way that prep did it, and it's more consistent.  It should roughly
match the available precision of floats and doubles.

though; need to figure out where the slowdown lies.

Add stream existence check to server's /intervals and /extract paths,
add tests for it.

Make start and end arguments optional for /extract, like /intervals

Move --quiet command line option to just the insert subcommand.
It's the only one that uses it right now, and otherwise it doesn't
show up in after a "nilmtool.py intervals --help".  Might revisit this
later if more commands start supporting --quiet.

Change cmdline/extract's write into a print, to keep the trailing
newline.

Fix lingering uses of Interval in nilmdb and change to DBInterval
instead.

Fix nilmdb interval bisection:
  - handle common case optimization correctly
  - db_endpos is always one after the last row, so use hi=db_endpos-1

Finish nlimdb stream_extract

Add a bunch of cmdline tests for extract, particularly testing border
cases around start/end.  Compares output to a set of files stored in
the tests/data dir.

Some more tests in test_client to get better coverage.



git-svn-id: https://bucket.mit.edu/svn/nilm/nilmdb@10893 ddd99763-3ecb-0310-9145-efcb8ce7c51f