Resource caching

[ForNeVeR]

trafficstars

Need to fix the HTML, CSS, file resource caching so they will be redownloaded after changes.

[ForNeVeR]

Here's an example of poisoned request from mr. @gsomix:

Host: fornever.me
User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:42.0) Gecko/20100101 Firefox/42.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
If-Modified-Since: Sun, 01 Nov 2015 12:27:27 GMT
If-None-Match: "5636052f-13b9"
Cache-Control: max-age=0

It seems that the old server have included Modified and E-tag headers, but the new server cannot process them properly and always return 304.

[ForNeVeR]

Currently there're issues only with static files. Maybe need to enable caching for the static file module.