and use it to avoid a warning in ./bootstrap.

Replaces (deprecated in OTP 25) http_uri calls with uri_string.

Fixed link to list of plugins.

Apparently the docs at rebar3.org do not contain the list of available
plugins - the docs at rebar3.readme.io do.

rebar_compiler: fix DAG and speed-up analysis for large repositories

This patch fixes incorrect behaviour of rebar_compiler_epp that
finds dependencies in _build/test/lib/... folder when rebar3 is run with
test profile. It is caused by code:lib_dir() pointing to _build
directory (when ebin is added to code path). Problem originates in
OTP that expects "include" and "ebin" directories being next to each other,
but rebar3 separates build artifacts and include files.

This patch also significantly speeds up analisys, caching file-to-application
mapping and avoiding repeated lookup for the very same gen_server/...

use newest certifi release

bump relx to v4.2.0 and rebar3 version to 3.14.3

Add support for relx config file

create release and upload escript for new tags

output relative paths in dialyzer provider

bump relx to v4.1.0

Prevent dialyzer warnings on OTP 23

We adapt .gitignore to the new vendored folder, also

1. we now rely on $1's vendor.sh script (instead of duplicating it here)
2. we assume that hex_core is rebar3-compatible
3. we rely on TARGET_ERLANG_VERSION
4. we generate exactly what was previously generating, while targeting a specific Erlang/OTP vsn

(some are not "wrong" per se, but incomplete)

Add a docker recipe for rebar3 itself

fix logger reset for the shell plugin

Re-vendor hex_core in at 0.7.0

The shell plugin has to reset the logger by fetching its configuration and
re-applying it later. In the current state, `maybe_reset_logger/1` will only
re-apply part of the configuration (the `config` key), which does not include
other settings such as filters and formatters.

The effect can be demonstrated by adding filters or formatters to `~/.erlang`
and running rebar3 shell on any project (without any --config argument, this
one reload the logger env; updating the kernel/logger environment in
`~/.erlang` fixes it).

For example:
```erlang
logger:set_handler_config(default, #{formatter => {logger_formatter,
                                                   #{template => ["> ", msg, "\n"]}}}).
```

This patch makes sure the default handler is re-created with its entire
original configuration.

Fix relup cmd arguments and add validation

relx:build_relup does not allow for undefined Release or ToVsn
so we verify that they have been given on the command line
before running relx:build_relup/4.