GitLab

* Break user guide into parts

* Break up file I missed

* Add basic .gitignore to suit out-of-tree builds in build, build1, build2 ... build9

* Small changes to autonumber.py for doc compilation

This is a small change designed not to fix the incorrect logic of
autonumber.py, but just to get the docs compiling. While assigning
numbers, the code now just ignores the autonumber_by_chapter
setting for a particular object if it can't find the appropriate
section in section_numbers. This is a temporary fix!

* Include part and chapter in autonumbered objects

* Fix autonumber.py to correctly reference autonumber roles in file-level sections

* Unify and simplify styling across documentation

* Break dev docs down into individual chapter-files

* Correct absolute links to relative

* Disable browser suggestions for lunrsearch box in API docs

* Remove part name from chapter 2.1

* Rename ambiguous 'Home' link to OpenMM.org

* Typo

* Minor fixes and reversions

Reverts some changes I had made and later thought better of,
and fixes some recurring typos across the documentation.

* Number developers guide chapters

* Fix responsiveness

* Remove header.rst and center captions

* Add a level of depth to main TOC and styling to accomodate

* Add third level to Part-level TOCs

* Use :numref: instead of :ref: to number links to sections

* Continuously number chapters in user guide

* navbar links to other docs relative, not absolute

* Improve navbar spacing with new template

* Fix sidebar while allowing it to scroll

* Hard -> Soft links for navigation.html template

* Add navigation.html template to cmakelists

* Add another level of .. to relative links

* Fix flex on C++ and remove layer of ..