127.0.0.1 -> 127.0.0.137 (to be less standard and so avoid clashes)

And removed V1 prefixes and suffixes from the rest of the storage code.

Use `/logfile.txt` instead of a query string to ease saving it or opening it
in some text viewer or editor.

Instead of closing the connection, as that prompted the UA to furiously
retry sending the same request many times.

It was causing crashes on Android

This adds several enhancements for HTTP store maintenance:

  - Removal of entries older than `max-cached-age`, as well as temporaries not
    seeing progress.
  - A periodic garbage collector for such entries.
  - Removed entries are no longer announced in the DHT.
  - Reporting of (approximate) local cache size in the status API and client
    front-end.
  - A button to purge the local cache in the client front-end.
  - Cancellable local cache iteration and cleaning operations.

Among other minor fixes, this allows the client to cache the URI swarm name
prefix, avoiding extra encoding every time it is needed.

To avoid having to build the whole name (which implies encoding the injector
public key) every time a URI swarm name is needed.

It was previously on some internal document.

This includes several fixes related with automatic swarm name computation:

  - Use lower-case, unpadded Base32-encoding for injector keys in swarm names.
  - Disable obsolete `announce-in-bep5-swarm` injector option in Docker
    wrapper script.
  - Show injector public key in the client front-end (to ease showing it to
    other users).
  - Also allow setting the injector public in Base32-encoded format for the
    `--cache-http-public-key` client option (to ease receiving it from other
    users in written form).

Padded or unpadded, upper or lower case.

Only explicit BEP5 swarm names conflict with automatic swarm name derivation.

The injector BEP5 swarm name is computed automatically now.

The injector BEP5 swarm name is computed automatically now.

This encoding is more amenable to human exchange shall we accept it as input,
so better start using it now and avoid having to change the general swarm name
derivation method further down the road.

Some operations on the whole store may take a while.

Because whether something is to be stored is implied by the use of the
fresh_channel::injector_or_dcache route.

It adds no value and only causes additional traffic. It is because if
the injector_or_dcache access fails, it implies that connection to the
injector failed. And if that is the case, than neither the ::proxy
mechanism will succeed in connecting to it.