PelEntryNumber::setValue() declaration fix

PelEntryNumber::setValue() must have the same declaration with its parent's, PelEntry.
Static context of Pel::[gs]etJPEGQuality() fix

In order to avoid error

Non-static method Pel::getJPEGQuality() should not be called statically, assuming $this from incompatible context
Merge commit '6c61373accd9f28f6ee4b2e5f8c6ff5e93d2566c'