use PRV_ERROR to wrap a provider error in {error, {?MODULE, ...}}

version in source dep element is no longer used, support leaving it out

Fixes for profiles breaking templates and installing of non-default deps

Partial fix to circular deps (#40)

- Adding tests
- fixing use of set fetching to find repeated deps and prevent infinite
  loops

On a circular loop rebar3 now fails with `{error, no_sort}`, which is
uncaught and should be handled to consider the issue fully fixed.

if already seen dep before don't try handling it again

Update error message and fix order of dir creation for deps

merge over rebar2 PR #401

change name of config for where project apps lib to project_apps_dir

only read in rebar config and lock of dep if needed

Support a list of ct_run results

Initial tests for dependency resolving

- Reworked the helpers for existing suites and expanded them
- Created a mock git resource module to test for its dependency fetching
- Added a test suite for dependency resolving with first checks for
  common cases (https://gist.github.com/ferd/197cc5c0b85aae370436)

Left to do would include:

- Verify warnings
- Verify failures
- Verify dependency updates resolving

API for Plugins (solves #22)

Profiles

- includes logging macros and turns them to functions
- exports customized types