Update CLI + Added a simpler interface for mining association rules

[zStupan]

• Updated CLI for the current interface (added metrics and weights flags)
• Added a --version flag that prints out the current version of the library
• Metrics: Yule's Q, netconf and conviction would throw division by zero errors, for rules with support 1. There are a lot of rules generated that are true for every transaction (the entire ranges of features would be selected). I just added a small value to the denominators to avoid this.
• Added the get_rules function which provides a simpler interface for mining rules, it.
• Added a RuleList class, which is a wrapper around a regular list of rules but you can get stats, sort rules by metric and export to csv. It replaces the stats class, and the rule sorting and export functionalities are moved to it from NiaARM
• closes Measure running time of an algorithm #26, since get_rules also returns run time.

[firefly-cpp]

Excellent work, @zStupan!