Renamed string extensions file to more meaningful name
Cache will not write to disk when contents matches existing file.

The ResourceCache is not to overwrite an existing file when the source
contents matches. Comparison done via CRC32 hash.
HttpApplicationBase to revert to virtual methods

HttpApplicationWrapper to set event proxies in constructor via a boolean
flag.
Unit test for Null HttpContext properties

Test for get access to Items and Request property on the HttpContext
object.
Find cache entry method changed to show intent

Find cache entry mathod to change from HttpContext to a Url which shows
the intent of the method and aids in unit testing.
Bug found in module where headers were being cleared after being set.
Removed unused usings, code formatting.
Resource cache unit test to skip existing entries

Existing resource entries that have previously been cached are skipped if
the desitination file exists.