Simplified advertisepipe to use locks instead of thread counting, and improved error handling. Also removed the functionality required for advertising newly added items immediately. (You'll have to wait REDO_INTERVAL/2 on average for new items to be announced now.) I may add this in again later, e.g. directly advertising from ```add_to_pipe```, despite the associated efficiency issues (larger number of threads created).
Addressing issue #137. Changed many files from using dy_import_module_symbols to dy_import_module. Also changed the code in appropriate places to reflect the new style of import.
Addressing Albert's comments for Pull request #144. Fixed a small bug and changed certain module object name to the full library name.
Fixed a typo bug in advertise.r2py
Merge branch 'v2' into seattlelib_ticket_137
Added `time_interface.time_getunixtime` to time.r2py.

Following the example of the other `time.time_*` functions, I
include `getunixtime` (defined in time_interface.r2py) to
time.r2py too. It thus suffices to `dy_import_module("time.r2py")`
to get access to the time functions.
Added missing module names to imports from `parallelize`.
Corrected indentation.
Band-aid to get seash imports and Affix overrides right. See SeattleTestbed/seash@35ec6398778ed8f242157e35408dd436334eb0ee for details.
Merge branch 'advertisepipe-should-not-die' into v2
Made advertisepipe advertise new items immediatey on `add_to_pipe`.

I'm using a single-threaded version of `advertise_announce` for
this to avoid spawning tons of threads if the node goes offline.
(Other modules' retry intervals and `advertise` threads' timeouts
can lead to a runaway condition.)

Also, minor refactor to use the constant `ERROR_RETRY_INTERVAL`
throughout.
Implement singlethreadedadvertise_announce, and update unit test for advertisepipe.

Also remove debug statements from the library, and give better
indications of what's going on in the unit test.
Merge branch 'seattlelib_ticket_137' into v2
Update unit test to show that nested imports and catching of exceptions work.
Make the testlib a proper (though boring) unit test too to avoid an error message.
"Ported" tcptime unit test to Repy, added test for new error message in time_interface.

* ut_seattlelib_tcptime.py used repyportability for no good reason.
* ut_seattlelib_time_interface_updatetime_before_registermethod.r2py
  verifies that tcp_time complains when you try to update the time
  before registering a method at all.