Always-on recursive application of all rebar commands causes too many
issues. Recursive application is required for:
1. dealing with dependencies: get-deps, update-deps, and compile of deps
   right after get-deps or update-deps
2. projects with a riak-like apps/ project structure and dev process

The vast majority of projects are not structured like riak. Therefore,
moving forward it's best to (by default) restrict recursive behavior to
dealing with deps. This commit does that and also adds command line and
rebar.config options for controlling or configuring recursion. Also, we
introduce two meta commands: prepare-deps (equivalent to rebar -r
get-deps compile) and refresh-deps (equivalent to rebar -r update-deps
compile). riak-like projects can extend the list of recursive commands
(to include 'eunit' and 'compile') by adding
{recursive_cmds, [eunit, compile]} to rebar.config.

- add missing short and long options
- add tests=, target_dir=, overlay_vars=

This change adds the ability to use alternate urls for downloading
dependencies. To make use of alternate urls run:
rebar get-deps alt_urls=true

Add no_debug_info option.
Remove debug_info=1 option.

Add generate-upgrade and previous_release=.

Also add a sleep after printing so that the io server has
written all output before exiting. It's a work around.

Add get-deps and delete-deps to commands info string and
bash completion script.

Add create command's template variable to bash completion.

Add -c/--commands option to the bash completion script.