upgrade erlware_commons, bbmustache and relx

Only have the port cd, not rebar3 as a whole

don't run unnecessary code if hooks are empty list

handle http:// git deps in check fif upgrade needed

ensure necessary directories exist to compile mibs files

always close port when done with it. fixes #589

Add proxy support to bootstrap and rebar3. Enhancement #561.

Changed cases on robocopy so it uses variables in a better way

Robocopy fix for different behaviour when copying/moving files and folders

Run agent as current process & hibernate

This tries to reduce memory usage when running `rebar3 shell` by running
the agent in the current process (and avoiding to copy state
cross-boundaries), and using frequent hibernation after each run to
force a full GC and compaction of the current process.

wip: deps install refactor

Minor refactors

remove `cover_print_enabled` and `cover_data_dir` config options and replace with `cover_opts`

Apply profiles properly & load all paths

and replace with `cover_opts`

The old run didn't necessarily apply all profiles well, and would only
reload modules in the app file. However, since adding extra_src_dirs,
modules can be compiled without ending up in the app file; this lets
the rebar3 shell agent handle that case.

update plugin template to separate plugin init and providers

add hex attributes to .app.src templates

Read and process .app.src.script if present

setup hex httpc profile and http opts. needed also for proxy