use standard, unassigned ports for the daemon

port 8080 is often in use on servers. it's the case here, and blocks that part of the daemon from starting up:

```
anarcat@marcos:~$ ipfs daemon
Initializing daemon...
API server listening on /ip4/127.0.0.1/tcp/5001
Gateway (readonly) server listening on /ip4/127.0.0.1/tcp/8080
23:18:02.772 ERROR cmd/ipfs: listen tcp 127.0.0.1:8080: bind: address already in use :24
```

[IANA](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt) allocated port 8080 to web caches:

```
http-alt 8080/tcp webcache # WWW caching service
```

...but it's frequently squatted by a hodge-podge array of random offenders (e.g. Icecast, in my case, Apache Tomcat, Syncthing, etc). ipfs is the latest addition to the stack. :p

5001 is allocated to an obscure:

```
commplex-link 5001 tcp
```

... but it is also used by `iperf` (oh that could be pretty fireworks), Slingbox and Synology, according to [Wikipedia](https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers).

the port should at least be customizable, maybe it is, but `ipfs daemon --help` doesn't tell me how.

i also believe a standard port pair should be requested from IANA, unless an RFC is made for HTTP/3 and the ipfs port becomes `80`. :p but maybe that's a separate issue?

at least finding less busy ports would be a good idea. according to wikipedia at least 8082, 8084 and 8085 are free if you like the 80XX range, and 5020+ is also free.

For more sources on ports:
- [IANA](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.txt)
- [Wikipedia](https://en.wikipedia.org/wiki/List_of_TCP_and_UDP_port_numbers)
- [FreeBSD's /etc/services](https://svnweb.freebsd.org/base/head/etc/services)
- [Debian's](http://sources.debian.net/src/netbase/5.3/etc-services/)