Group dialyzer warnings by file and concentrate output

[Licenser]

Some more improvements on output, it's now easier to spot the file / line number the warning is in those are coded cyan. Also warnings are grouped by file now and the filename is only printed once.

This combination allows for a more concise output while staying nicely readable.

[ferd]

How does Cyan look on a white background?

[Licenser]

As good (or bad) as the green, actually I find it a bit better then the green ;)

[ferd]

Yeah I guess that's workable.

[fishcakez]

Is this length still correct? Should use length(Warnings)?

[Licenser]

length is still correct, but that said it still might be more sensible to use length(warnings)

[fishcakez]

Should file warnings be the new format, just without colour?

[Licenser]

@fishcakez file warnings use the dialyzer formatting to not break automatic processing of the output

[Licenser]

Failing suite is this: I'm confused how this

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rebar_src_dirs_SUITE:src_dirs_in_erl_opts failed on line 76
Reason: {badmatch,{error,
    {rebar_prv_app_discovery,
        {mul...}
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src_dirs_in_erl_opts(Config) ->
    AppDir = ?config(apps, Config),

    Name = rebar_test_utils:create_random_name("app1_"),
    Vsn = rebar_test_utils:create_random_vsn(),
    rebar_test_utils:create_app(AppDir, Name, Vsn, [kernel, stdlib]),

    RebarConfig = [{erl_opts, [{src_dirs, ["foo", "bar", "baz"]}]}],

    {ok, State} = rebar_test_utils:run_and_check(Config, RebarConfig, ["compile"], return),

    ["foo", "bar", "baz"] = rebar_dir:src_dirs(rebar_state:opts(State), []).

I'm not sure how this is related.

[tsloughter]

You'll need to rebase.

[tsloughter]

Cool. @ferd you good with this?