sql for benchmark db objects, code style improvements, and fix to portfolio_contents in python app

new relation in db: Analysis

Analysis stores information (risk-free rate, benchmark returns) that is
useful for calculating MPT stats.

"BENCHMARK_CONTENTS_TYPE"
Each instance represents one holding in the total benchmark.
Instantiated with strat_id, security, and allocation as parameters to
constructor.

"BENCHMARK_VALUES"
Contains the aggregate contents of the benchmark.  Total value is
calculated upon initialization.
Parameters: VARRAY of BENCHMARK_CONTENTS_TYPE, time

"HELPER"
Simply populates the portfolio_value and risk_free_rate in the analysis
relation.
Parameters: time, strat_id, analysis_id