Http: Handle empty or non-existing 'Last-Modified' header sent from the server. This means we cannot do any sensible caching and the data is always fetched from the server.
MaterialParser: Allow invalid ogre material lines where there is no value for a key. These properties will be skipped but wont be a fatal error for the material as a whole.
Http: Support parsing RFC 850/1036 format date headers. These should be extremely rare nowadays, were used in HTTP/1.0, but good to support anyway.
MaterialParser: Clarify in warning message that we are only skipping this one invalid token.
Merge pull request #4 from realXtend/master

Merge in commits from master