Property dispose proxies from external modules.

If we do not dispose the proxy templates, they will now
inherit from a proxy (KrollProxy) that is no longer valid
when the application and runtime restarts. This leads to missing
methods such as "addEventListener", "getProperty", etc.

[TIMOB-13620]
Merge pull request #4280 from joshthecoder/TIMOB-13620-3_1_X

[TIMOB-13620] Property dispose proxies from external modules.