Implement known values of Si, Ci, Shi, Chi at oo and -oo
Tests for values of Si, Ci, Shi, Chi at oo and -oo
Replace 0 by S.Zero
check_assumptions(): handle only bool values.

Assumption dicts only have values in {True, False, None}, so
there is no reason to complicate the code by special-casing
anything else.
check_assumptions(): Don't use new-style assumptions.

There is no guaranteed correspondence between old and new
assumptions with the same name.
Fix RootOf assumptions.

Fixes issue 3551.
Update doc/README.rst
Update doc/Makefile

Use foreach instead of  a bash for loop, thus stopping on the first error.
tutorial: formatting only.
tutorial: Update link to extended installation instructions.
Update tutorial.pot
Update tutorial.??.po
Update tutorial.zh.po
Doc formatting.
Fix typo.
Make sure Sphinx extensions are put in the front of the PATH
add subfactorial function
tweak docstring eqns
Merge pull request #1691 from rlamy/real-solve

Fix issue 3551
Merge pull request #1693 from jrioux/documentation

Documentation

Update the link to extended installation instructions in the tutorial. Clean up the formatting of the doc a bit. Update the translations and make sure that make html reports failure on the first error encountered.