Moved default location of TZP toolbar button from add-on toolbar to "toolbar" (navigation toolbar).

The add-on toolbar is scheduled to be removed from Firefox in a few versions.
And the change is necessary for it to work in Seamonkey.

Tool will appear as the last tool in the navigation toolbar.
Added ability to work in the Seamonkey application (which includes a mozilla browser).
Fixed javascript warning: yield => yield undefined
Version 2.7beta1; compatible with ff 28.0a1