Deprecate implicit thread-local currentPage, add implicit Page arguments where lacking

[nafg]

Convenient sometimes, but then surprisingly things don't work, when updates come from outside that page's thread (either server push, or by a user interaction on another page).
More importantly, a lot of methods in reactive call methods that take an implicit Page but don't themselves take one. By (at least temporarily) deprecating currentPage, the compiler will reveal the trail.

Perhaps currentPage doesn't need to be removed, and we can just leave the @deprecated annotation in order to generate compiler warning messages.

Does anyone think that this should bump the version number?

[nafg]

Fixed in 7b74048