Add basic decryption to ESDL script mysql operation

Acknowledging that it is barely better than embedding plain text passwords in ESDL scripts, add a mechanism for plain text passwords to be replaced by a value encrypted using the default encryption historically used in platform configuration files.

This is a (hopefully) short term crutch for customers unable or unwilling to use secrets. Use of this should not be encouraged, and it should not be included in documentation without a very strong warning that it is not secure.