Update intersphinx links and others

[woodsp-ibm]

Summary

Updates links away from qiskit.org to the new locations for the docs

Fixes #740
Fixes #741

Details and comments

Now that all the applications and the algorithms docs are deployed on github pages this updates the intersphinx links, in conf.py, and also urls that are coded directly in other places such as the readme and tutorials. I did not alter past release notes. There is a redirect now in effect for the former location on qiskit.org/ecosystem so they get to the right place.

Note that the current theme is still emitting a link to qiskit.org/ecosystem, but that will get redirected for now until such time as Qiskit/qiskit_sphinx_theme#588 is resolved and new docs are generated with such an updated theme and re-deployed.

There is one additional change in the readme, which I noticed, where it talked about the Fidelity algorithm introduced in Qiskit where I changed that to ... in Qiskit Algorithms

[coveralls]

Pull Request Test Coverage Report for Build 7717641653

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.567%

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Totals
Change from base Build 7700314664:	0.0%
Covered Lines:	1868
Relevant Lines:	2018

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💛 - Coveralls