Move JTB::assertJsCondition() to JSWebAssert, deprecate old

Problem/Motivation

assertJsCondition() should follow the path of assertElementVisible() and assertElementNotVisible().

That is, it should be deprecated and moved to JSWebAssert, so it's not nearly as confusing as to why it's there and not on JSWebAssert alongside other assertions with messages.

Proposed resolution

Move, deprecate.

Remaining tasks

User interface changes

API changes

Data model changes