Fix typos in strings and comments

[dforsi]

Those typos were found with codespell which is available from
https://github.com/lucasdemarchi/codespell.git

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---

What does this PR do and why is it necessary?

This PR fixes some misstypings in user-visible messages, in strings that go to log files and in comments.

How was it tested? How can it be tested by the reviewer?

Tested executing the unit tests and running the server.
Visual inspection of the colored diff here in github shows that only single words were changed.

Any background context you want to provide?

While these are trivial mistypings, having them fixed means that searching through the source will not miss these words and future runs of codespell are more likely to show if anything has changed

What are the relevant tickets if any?

Screenshots (if appropriate)

Further notes

I am submitting only changes to strings excluding vendor source files (eg. jQuery) and I did not change the following lines because "managable" is an object property (just let me know if you think it makes sense to replace all these occurrences with the word "manageable"):

src/octoprint/plugins/pluginmanager/__init__.py:463: managable  ==> manageable, manageably
src/octoprint/plugins/pluginmanager/__init__.py:464: managable  ==> manageable, manageably
src/octoprint/plugins/pluginmanager/__init__.py:963: managable  ==> manageable, manageably
src/octoprint/plugins/pluginmanager/__init__.py:963: managable  ==> manageable, manageably
src/octoprint/plugins/pluginmanager/templates/pluginmanager_settings.jinja2:50: managable  ==> manageable, manageably
src/octoprint/plugins/pluginmanager/static/js/pluginmanager.js:231: managable  ==> manageable, manageably
src/octoprint/plugin/core.py:145: managable  ==> manageable, manageably
src/octoprint/plugin/core.py:589: managable  ==> manageable, manageably
src/octoprint/plugin/core.py:651: managable  ==> manageable, manageably

[foosel]

Thank you! And sorry for the delay in merging this, first I was on vacation, then just when I was starting to catch up on the backlog I got sick (and I'm still recovering from that) :/

For now I'd say let's leave the manageable issue as is, exactly due to the reason you already stated. Backwards compatibility and all that. At least this won't be the first time such a misspelling makes it into an API ;)