May be used in case someone needs to log RPC exchange on the node side.

When tests/__init__.py is present, pytest adds root directory to
PYTHONPATH, so tests can use imports `from dexbot.foo import bar`;
otherwise, `pip install -e .` is needed. See doc for details:

https://docs.pytest.org/en/latest/goodpractices.html#choosing-a-test-layout-import-rules

This is a workaround for
bitshares/python-bitshares#234

Closes: Codaone#614

Closest order caclulation was a bit wrong which caused an error with new
in-memory caclulation logic.

Prevent moving liquidity away from center in valley and neutral modes.

Closes: Codaone#444, Codaone#586

Don't allow too small increase steps in mountain mode. This will reduce
number of calculations.

Closes: Codaone#585

Because we're now calculating increased orders in memory, it's a good
idea to reduce min_increase_factor to allow more smooth distribution of
profits.

Some tests were broken after increase logic related changes, this fixes
them.

test_increase_order_sizes_neutral_smaller_closest_orders is working if
some approximation allowed.