Fixes#1800
* Refactored duplication of code between OpCopyMemory and
OpCopyMemorySized validation
* Fixed some bugs in OpCopyMemorySized validation
* Replaced asserts with checks
* Added new tests
* Refactored the Memory class of instructions in the spec out Id
validation and into a new pass
* Tests unmodified
* some minor disassembly changes
* minor style changes