Adding basic tests for OP_CSV inside of script_tests.json
Changing NOP3 op name to OP_CHECKSEQUENCEVERIFY, renaming instances of OP_NOP3 in script_tests.json to CHECKSEQUENCEVERIFY
Cleaning up NOP3 comment
Re-adding test cases that were accidentally deleted, removing dupicated test case, fixing formatting
Removing re-labeling of OP_NOP3 to OP_CSV
Fixing whitespace issues