ThanksCount insight and CriteriaMatchInsightPluginParent

CriteriaMatchInsightPluginParent is a parent class for insights which look at some posts
    and track the change in how many posts match something over time.
InsightBaselineDAO::getMostRecentInsightBaseline() is added to support this.
ThanksCount is an implementation that looks at thankful posts.

ThanksCount copy tweaks

Capitalize network names in copy.
Change 1 time to once.
Split headline into two options.

Update CriteriaMatchInsightPluginParent and ThanksCount

Add docblock about parent class.
Add more variety to ThanksCount output.
Use getOccurrencesAdverb.

Thanks count - register insight, improve copy

Update thankscount postmatcher to exclude self-replies and updated headline

Only show %username %posted X thanks when there is a thankee.