Correct mix liquidity value for separately generated monthly graphs

[petrs]

The generation of monthly graphs is parallelized, so each month starts from 0 base value.

Split parallelization into two steps:

1. Computation of vectors with values with basis 0 for all intervals (parallelized)
2. Correct mix liquidity vector based on previous intervals (serial)
3. Plot resulting graphs with mathplotlib (parallelized)