Outdated models not cleaned

[haoyang-finix]

Current code generation script does not clear the model directory before running code generation. As a result, legacy models created older specs remain in model directory. One example is the risk profile models.

Fix:
add at the beginning of generate.sh command to clear the model directory (i.e. delete all files in that directory except for hand-written models that won't be autogenerated and should be kept)