[FEATURE] Make settings configurable via constants about fe_change_pwd

[derhansen]

From my experience from many of the projects I've been in, integrators often simply use TypoScript setup directly instead of using constants. But I agree, that having all settings available in constants would not break anything and could be an improvement for the extension.

If you like, feel free to provide a PR (v12 version only).

[derhansen]

• For v13, some TS settings needed to be moved to site settings. Those settings are also available as site set, which most likely will be editable with a GUI in TYPO3 backend at some point (unsure if this will be in v13 or later).

• The remaining TypoScript settings are related to the extbase plugin only. I did not see any reason to provide constants here and since no PR was provided, I will now close this ticket.