Add page counter

[jamesmontalvo3]

Adds two tables for counting number of hits to pages:

• wiretap_counter_alltime: counts the all-time number of hits to each page
• wiretap_counter_period: counts the number of hits to each page over a given time period (between X days ago and present). This is configurable with $egWiretapCounterPeriod = X;

On each page load either or both of these counters can be updated by setting these two variables:

• $egWiretapAddToAlltimeCounter = true; // defaults to true
• $egWiretapAddToPeriodCounter = true; // defaults to false

$egWiretapAddToPeriodCounter defaults to false because the "period" table requires the use of the wiretapRecordPageHitCount.php maintenance script to periodically clear out the table and refresh it with data from the wiretap table. Without this refresh (which should be done fairly regularly via a cron job) the period-table data gets out of date.

Additionally, both tables have a count_unique field that counts how many unique hits each page has gotten. This is also only provided by the maintenance script.

[jamesmontalvo3]

Won't really be able to test this until it's on ops. Appears to be working on local wiki. Merging to master, will re-test next week.