Skip properties directive if there are no properties

Refs #9562
Add an empty index file as Sphinx needs one to run successfully.

Refs #9562
Fix deprecated algorithm reference link.

Refs #9562
Disable QtAssistant for documentation transition

Refs #9562
Update README regarding images.

Refs #9562
Use ImageNotFound.png when no image available.

Refs #9562
Fix categories output to allow a namespace.

Refs #9562
Pull out wiki sections from cpp files and convert them to reST

The converted text is stored in separate .rst files in the docs directory.
Refs #9562
Move images from qtassistant directory to Sphinx source directory.

Refs #9562
Rename aliases directive to alias

Refs #9562
Fix image links in some rst files

Refs #9562
Standardize heading characters

Uses # to denote a html h3 heading.
Refs #9562
Disable screenshot generating in doc-test mode.

They are not necessary and they slow down the build quite considerably.
Refs #9562
Add global doctest setup code.

Runs the given code before each test is executed.
Refs #9562
Add usage examples to Rebin.

Refs #9562
Wire up alias directive correctly.

Refs #9562
Fix ..code directives to correct ..code-block

Refs #9562
Fix generation of redirects.

It no longer tracks algorithms as each build doesn't necessarily
go through every file. It just uses the factory to construct redirects
for everything.
Refs #9562
Fix algorithm page references

The page reference must be before the page title so that it can be
referenced without including the link text.
Refs #9562
Fix internal algorithm links.

The first underscore is not included in the reference name.
Refs #9562