Custom logic for stat mod calculations + Disabling SRD monsters + False statements in Property Line + footerEntries from 5etools

[kylomax]

Added #48 and #57 Fixed #67 and #78

This is only a half fix for #78. This only adds the footerEntries of some of the 5eTools monsters. The ones with footerEntries in variants were not added (though I believe variants are already not supported anyways).

[kylomax]

Hold off on merging, having some problems all of a sudden I wasn't having when testing it before.

[kylomax]

Alright, should be good now!

[kylomax]

@valentine195 This should also close #57 as well as #48. Half fix for #78, whether or not this is considered a fix is up in the air.