Disable spellcheckers from inspecting the password

[adamatan]

What does this PR aim to accomplish?:

Prevent password leakage by spell checkers.

How does this PR accomplish the above?:

Adds an explicit spellcheck="false" attribute to the password field.

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[yubiuser]

Thanks for your PR. Could you please rebase on latest devel?

[adamatan]

Thanks @yubiuser , done.