Utilities/Sphinx: Add option to build 'singlehtml' format

Add SPHINX_SINGLEHTML to enable the Sphinx 'singlehtml' builder.
Merge branch 'master' into doc-singlehtml

Resolve conflicts in Utilities/Sphinx/CMakeLists.txt by adding the help
options from both sides.
Restore --help-full option to output all help manuals

This option was removed during conversion to the reStructuredText
documentation.  Restore it.  Process documentation starting at
Help/index.rst so that all manuals are included in the output.
CMake Nightly Date Stamp
UseSWIG: Add support for Go and Lua
Merge topic 'doc-full-help'

478356e6 Restore --help-full option to output all help manuals
Merge topic 'doc-singlehtml'

aaa6c8a6 Merge branch 'master' into doc-singlehtml
faf291a9 Utilities/Sphinx: Add option to build 'singlehtml' format
Merge topic 'UseSWIG-go-support'

a3b1be5e UseSWIG: Add support for Go and Lua
ninja: Use string parameters
ninja: Don't use a stringstream to build an argument list

Streams are expensive to construct (looks like some locale-related
stuff), so use strings instead.
LocalGenerator: Add a string overload for AppendFlags
ninja: Factor out target-level order-only dependencies

This reduces ninja file output even more for projects with lots of
libraries with entangled transitive dependencies. ParaView goes from the
previous 58M to about 45M.
ninja: Factor out custom command order-only depends

This makes WebKitGTK's CMake build.ninja file go from 165M to 11M and
configure/generate in 5 seconds.
ninja: Store target-level flags in a variable

This greatly reduces the size of Ninja files projects with lots of flags
and lots of source files in libraries. ParaView goes from 110M to about
58M.
ninja: Factor out target-level definitions

Worth another 3M in the WebKit build.ninja file.
ninja: Fix and refactor variable name escaping
ninja: Factor out language flags into a variable