- and add python*-all

In Python 3, `PyArg_ParseTuple` and friends can return either an int
or a Py_ssize_t type for the length in an argument of the form
`"s#"`, `"y#"`, `"u#"`, etc, controlled by whether the preprocessor
macro `PY_SSIZE_T_CLEAN` is defined when the header `Python.h` is
included. A future version of Python will only support `PY_SSIZE_T`.
In Python 3.8, there was a deprecation warning added (see
https://bugs.python.org/issue36381).

Define the `PY_SSIZE_T_CLEAN` macro to suppress the hundreds or
thousands of deprecation warnings that may be printed when reading
a LIGO_LW file.

See also lscsoft/glue!69.

- merge append_process(), append_process_params() and process_params_from_dict() together into register_to_xmldoc()

- rewrite the documentation related to encoding of +/- inf
- add support for +/-inf to gpsproperty_with_gmst

- with it, add additional sanity checks to I/O code
- add documentation, doctest unit tests of all of this code

- transform some of the logic into methods of classes in lsctables.
- get_username() is converted to a static method of the ProcessTable class
- the Process class gets a .initialized() class method to create one with sensible defaults copied from the append_process() function in process.py
- process.py's append_process() is replaced with a wrapper around the new method
- set_process_end_time() is turned into a wrapper around a new .set_end_time_now() method added to the Process class
- process_params_from_dict() + append_process_params() together are made to rely on the .pyvalue machinery of the ProcessParams class to choose the correct type string, removing all of that code from process.py
- ProcessParams's .append() method's invalid type string check is made to be more verbose to help debug problems
- delete abandoned register_to_ldbd()

- .handle_request() causes the server to exit after one request, so there's no need to try to kill it we just have to wait while it exits on its own.
- also, port the server instantiation to python 3 modules and remove the use of six from Makefile.

- contained a reference to an outdated function that no longer exists.

- allows a conflict to be broken when both python2 and python3 versions are built.

- nothing ever used it except the DBTable class, which ran a .commit() on the database.
- the .commit() is more easily implemented as a .endElement() override in a custom Stream handeler, and I've never figured out if the .commit() is even beneficial at all.
- this patch removes the hook, leading to a *miniscule* performance improvement loading documents, and a conceptual simplification of the code.

- .snr_geometry_factors()
- .effective_distances()
- .expected_snrs()

- found an old error message directing people to e-mail the glue maintainer.  update.

- SnglInspiral doesn't have .get_end() method anymore

These directories are produced by Python 3 to store bytecode.

- txt file required for tests is missing from distributions

- fix error in defintion of .segment property:  use segmentproperty(), not gpsproperty()
- fix typo in documentation