Also expose it in rebar_api

Breaking up initial call to parse from the ones deep inside the provider
parsing to do smarter namespace detection, added 'as' the ability to
look into these also, and cleaned up the code a whole lot that would
depend on implicit assumptions.

A side-effect is that 'do' is now valid for all namespaces, although it
can be overriden.

error before:

===> Uncaught error: {'EXIT',
                             {badarg,
                              [{io,format,
                                [<0.23.0>,
                                 "\e[0;36m===> Skipping template ~p, due to presence of a custom template at ~s~n~n\e[0m",
                                 ["/home/mariano/.config/rebar3/templates/fn_app/fn_app.template"]],
                                []},
                               {rebar_templater,prioritize_templates,2,
                                [{file,"src/rebar_templater.erl"},{line,330}]},
                               {rebar_templater,find_templates,1,
                                [{file,"src/rebar_templater.erl"},{line,274}]},
                               {rebar_templater,new,4,
                                [{file,"src/rebar_templater.erl"},{line,47}]},
                               {rebar_prv_new,do,1,
                                [{file,"src/rebar_prv_new.erl"},{line,44}]},
                               {rebar_core,do,2,
                                [{file,"src/rebar_core.erl"},{line,129}]},
                               {rebar3,main,1,
                                [{file,"src/rebar3.erl"},{line,46}]},
                               {escript,run,2,
                                [{file,"escript.erl"},{line,752}]}]}}

root project

get correct compile paths included in module info

This adds some more convolution to command parsing, unfortunately, but
makes some cases clearer (`rebar3 as as as as` is no longer valid). It
unfortunately disallows using $REBAR_PROFILE along with `as` in a rebar
command.

fixes #238

* Return error on failed and/or auto skipped tests
* Print all results for quiet repeated tests
* Sum results of repeated tests

Previously dialyzer stored the project PLT in ./build/, which meant the
same PLT was used for all profiles. This could mean partial rebuilding
of a PLT when switching between profiles.

fixes #216 and #220

rebar state from propogating appropriately

to `as` used to generate them

- fetch more complete refs for tags (may download more history than
  required, but it works)
- Fix comparison of tag distance by using lists everywhere

pre-purging before checking to facilitate long do chains

source files in the `compile` key of `module_info/1` so `rebar cover`
struggles locating source in some instances. in these cases a warning
is printed and crappy coverage info is written rather than none at all

`rebar.config` or via the `-c\--cover` flag given to the appropriate
task) from the `eunit` and `ct` tasks and add a `cover` task to
write coverage analysis to disk