Workaround to avoid crashing bbPress' frontend profile page

[CryoutCreations]

This workarounds skips the addition of the TwoFactor fields to the user profile when it's part of bbPress' frontend profile edit page. These are settings that shouldn't probably by editable on the forum profile anyway.

Fixes the Fatal error: Uncaught Error: Call to undefined function convert_to_screen() reported in #175

Frontend profile page error example:

[CryoutCreations]

Per @kasparsd's request I moved the bbPress conditionality check to the two-factor-compat class and changed the function call to use a more general function.

Hopefully the code now meets the logic separation requirements.

[jeffpaul]

Per yesterday's bug scrub, while we want to be compatible with official plugins we're going to punt this to a future release so that the 0.8.0 release can focus on the U2F deprecation.