Updated URL for connectivity check during installation

Updated the URL for connectivity check via fopen/cURL to the update.xml
file on the new evekb.org server (still pointed to the EDN logo on
eve-id.net).
copy/paste cleanup
Comments not diplayed on kill detail pages

- Method is called statically in `common/xajax/xajax_core/xajax.inc.php` but not defined as such.
Fix: zKB fetch not fetching new kills

Fixed a bug with the negative time offset, causing zKB fetch to fetch the
same 200 kills all over again if there were more than 200 kills within the
offset timeframe.
Now a second fetch cycle is done until an empty result or a new result
gets returned (or the safety limit is hit).
Enhanced error logging for API import/IDFeed
Fix for external Character ID sanity check

There was a way to create a Pilot object with a valid external ID that
would return 0 as external ID when called getExternalID().
Fix: Updated XHTML theme for CREST link posting
Fix: Correctly distinguish involved structures

Fixed a bug causing Control Tower belonging to Corp A as final blow pilot
on a kill where Control Tower belonging to Corp B actually laid the final
blow. This error could be observed in kill list tables and top lists.
Fix: zKB fetch fetching the same kills all over again

Fixed a bug causing zKB fetch to fetch the same bunch of kills until it
hit the maximum cycle count.
Occurred if all kills returned had the same timestamp.
Fixed formatting of zKB fetch error texts
Enhancement: Added compression to SimpleCrest cURL fallback

If zlib or pecl is installed, the Accept-Encoding HTTP header is set to
"gzip" for cURL fallback method (file_get_contents).
This fixes the problem with zKB fetching without having cURL available
(zKB API now requires to either use gzip or deflate as compression).
Feature: CREST item value fetcher

Replaced the old item value fetcher (depending on an external source for
item prices in XML format) with a fetcher for CREST average market prices
(using endpoint https://public-crest.eveonline.com/market/prices/).
This endpoint is updated daily and contains the same prices used ingame to
display item values.
Updated CCP DB to Phoebe 1.0 (build 107269)
Updated README and checksums for R4.2.5.0