hashing in TAssetManager

[xue]

Shorter path definitely looks better.

What is the collision rate comparison between crc32 and md5?

I suggest using 8 characters (hexical representation of crc32), which can be done by simply a call to sprintf('%x',crc32($value));

I did a small profiling. For 1000 calls of hash, the current implementation takes about 0.06sec, md5() takes 0.008sec, while using the above 8 chars approach it takes 0.004sec.