Rex::Logger improvements

[kablamo]

Synopsis of changes:

use Rex;
use Rex::Logger qw/:all/;

log_debug("doing a thing");
log_info("boop");
log_warn("the core is in danger of meltdown");
log_error("the core melted");

[ferki]

Do we really need Exporter::Shiny as a new dependency? :)

[kablamo]

• removed Exporter::Shiny dependency even though its awesome 😭
• warn() is a perl builtin so all methods now start with log_. Probably makes more sense to have a verb in the func name anyway.
• force pushed
• ready for review

[ferki]

I'm afraid this breaks existing Rex::Logger::info calls in the wild, at least when they specified warn or error levels :/ Am I missing something? Maybe I'm mistaken, didn't test it yet.

[kablamo]

Updated to make call to info() backwards compatible. As we agreed on irc this doesn't need to be merged until the next release. Ready for review though.