swarm/storage/feeds: Renamed MRU to Swarm Feeds

swarm: handle errors in cmdLineOverride and envVarsOverride

cmd/swarm: correct swarm version on --help

cmd/swarm: disable export and upload tests on Windows

- Mime types generator (Standard "mime" package rely on system-settings, see mime.osInitMime)
- Changed swarm/api.Upload:
    - simplify I/O throttling by semaphore primitive and use file name where possible
    - f.Close() must be called in Defer - otherwise panic or future added early return will cause leak of file descriptors
    - one error was suppressed

This implements EIP-695.

- update go-colorable, go-isatty, go-runewidth packages
- use go-isatty instead of log/term and remove log/term package

When CLI tests were spanning new nodes, the log level verbosity was
hard coded as 6. So the Swarm process was always polluting the test
output with TRACE level logs.

Now `go test -v ./cmd/swarm -loglevel 0` works as expected.

I am planning to use this to resolve names to user addresses for Swarm/MRU feeds.

cmd/swarm: trim new lines from files