Download network dapps and load them from filesystem (#144)

* Download network (registry) dapps and load them from filesystem

* Remove obsolete Rust files

* package-lock.json

* Linting

* Fix tests

* Lint

* Fix .includes() is not a function (:88)

* Remove rust files from CI build

* Update @parity/ui dependency

* Grumbles

* Restrict in-frame navigation for dapps (#146)

* Restrict in-frame navigation for dapps

* Lint

* Grumbles

* fs-extra pathExists doesn't throw if the path doesn't exist

* Fix bug uglifyjs