go1.4: migrate "code.google.com/p/go." to "golang.org/x/"

Signed-off-by: Tom Grennan <tom@apptimist.co>
wild-cards, cli, clone, time...

- Introduce '$', and '~' prefaces for respective blob sum and user references.
- '$*' wild-card for all blobs
- '~*' wild-card all users
- '~.' wild-card local users (those that have marked on the session server)
- mark w/o LAT/LON or PLACE clears an earlier mark
- asnadm now has a readline cli (no completion yet)
- implement indirect clone of a server from another
  this queries blobs after any given date to fetch the remainder
- @TIME spec may include decimal or hex UnixNano, date or duration strings

Signed-off-by: Tom Grennan <tom@apptimist.co>
add filter command

usage: filter FILTER [ARGS... --] [BLOB...]

The filter command acknowledges with the output of the FILTER program with the
list of newline separated blob filenames as the program input.

Signed-off-by: Tom Grennan <tom@apptimist.co>