* Dapps web

Conflicts:
	dapps/src/apps/fetcher.rs
	dapps/src/handlers/fetch.rs

* Rewriting fetch

* Parity-wide fetch service

* Obey the limits and support cancellation.

* Removing temporary files.

* Actually use Fetch for dapps

* Re-implementing file fetching to avoid temporary files.

* Serde to 0.8.19

* Fixing content & dapps fetch