Phrasedml

Build redesign, plus various smaller bugfixes.

Build redesign:
* Use ctypes for python bindings, so we don't have to compile with SWIG for every combination of Python and OS.
* Push dependencies to libroadrunner-deps, so we can use that directly.

Bugfixes:
* Use newer KiSAO terms.
* Allow negative start times.
* Write SBML namespace into SED-ML file.

* Fixed a segfault that occurs when loading certain types of model changes.

* Fixed https://github.com/sys-bio/tellurium/issues/224

Changes:
* Allow more general xpath queries for changing model variables (in order to be able to read example 1 from https://bmcbioinformatics.biomedcentral.com/articles/10.1186/s12859-014-0369-z)
* Fix https://sourceforge.net/p/phrasedml/tickets/21/ with string substitution hack