Remove -Wunderspecs from default generated dialyzer options

Also pruning the list of OTP apps to include in ~/.dialyzer_plt
Removing apps that are less commonly built upon for a speedier build.
Add devrel target

Eventually this won't be required or can be very much simplified as relx
will handle it.
Cleanup shell target

Don't enforce the dependency on compile and eunit. The common case is to
start the shell after you've seen a test fail, so just do that b/c it is
faster.
Add support for dep locking via rebar_lock_deps_plugin

* If a rebar.config.lock file is present, it will be used with the
  exception of the prepare_release target and its friends.

* The allclean target is enhanced to detect with the rebar in play
  requires a -r flag or not to clean all deps.

* Fix bad copy/paste hard code in newly added devrel target

* Add prepare_release target with relx integration

* Generated rebar.config now includes {use_lock_deps, X}. X defaults to
  false for non-active projects and true otherwise. It is also possible
  to specify a branch or tag of the rebar_lock_deps_plugin here.

* Refactor cleanup of generated rebar.config.script. Incremented version
  to 2. Adds support for optionally including rebar_lock_deps_plugin.
Merge branch 'sf/lock-deps'