Rewrote changes from Brian 1 + minor changes
Moved some stuff from user guide to advanced
Updates to user guide and additions to advanced guide
Added Cython example to adding functions user guide
Added ability to do quick rebuild (no rebuild on examples and reference
docs)
Reorganised and added placeholder for getting started guide
Finished getting started guide
Added SpikeGeneratorGroup
Added docs on monitors
Improved preferences documentation
Moved old notes to known issues
Start cleaning up dev docs
Added How Brian Works section
[ci skip]
Added new developer codegen docs (not quite finished)
[ci skip]
Merge branch 'master' into docs_improvements

Conflicts:
	docs_sphinx/developer/index.rst
Fixed a few issues with openmp documentation
[ci skip]
Do not fake private/magic attributes in `CurrentDeviceProxy` -- gets rid of a number of warnings when building the documentation.
Various small changes to the user guide
Docs on computation added
Merge branch 'docs_improvements' of https://github.com/brian-team/brian2.git into docs_improvements