Also some improvements to error handling has been done. Trying to get rid
of as much of eval's as possible in cases where it's used to load a module.

- Another significat change is introduction of attrs attribute on
Foswiki::Configure::Item objects. It is used to hold all serializable keys
– i.e. those which names are not started with underscore. This is somewhat
of a headache across the Configure code because previously all keys were
stored directly on the object hash. Now non-serializable keys must have
their own attributes (like _parent, for instance). For example, old code:

$item->{serializable}
$item->{_nonserializable}

must be replaced with:

$item->attrs->{serializable}
$item->_nonserializable

Perhaps the children key shall get its own attribute too but I left it for
later.

- Moved redirect() method to Foswiki::App.

- Improved Foswiki::Config localization code by localizing not only data
but files and urlHost attributes too.

- Added TO_JSON method to Foswiki::Exception to take care of cases when
eval hides a thrown exception and interprets it as a response for a JsonRPC
request. This happened to Store::Implementation checker code leading to
JSON failing to encode response object.

- Added Foswiki::Exception::errorStr static method to convert an error
object of unknown type (i.e. a string from die, or a Foswiki::Exception or
Error descendants) into a plain string. For blessed references it is using
stringify or text methods in the order given.

- Fixed a bug in store encoding checked which was causing a regexp match
agains unitialized {Store}{Encoding} key during bootstrapping stage.