Allow more PHP functions in validation class

[Maxximus]

At this moment it's possible to use trim(), md5() and sha1() as a rule in validation. It would be nice to allow several other functions as well, like strtoupper(), ucfirst(), ucwords() etc.

At this moment it's not possible bcz. such a rule is treated as a result function, and will not alter the data field itself.

[armen]

Fixed in r1536

You can use php functions like trim, sha1, md5, strtoupper, etc as a rule, just add an = at the beginning of the rule name.

*BC Break* : you can't use trim, sha1 and md5 rules anymore, you have to add an = as prefix