Simplify configuration needed for setup tap / tarantool tests

[Totktonada]

core = tarantool tests:

• use default .tarantoolctl when there is no .tarantoolctl
• use default script (e.g. master.lua or app.lua) when there is no one

all tests:

• add recipe how to integrate test-run into the new project, like so:

In project dir:

git submodule add https://github.com/tarantool/test-run.git
mkdir test && cd test
ln -s ../test-run/test-run.py ./
cd -

In Makefile:

.PHONY: test
test:
    virtualenv -p python2.7 ./.env-2.7
    source ./.env-2.7/bin/activate && \
        pip install -r ./test-run/requirements.txt && \
        pip install tarantool && \
        cd test && ./test-run.py

[Totktonada]

The first bullet is implemented in PR #242.