Improve SecurePolicyWriter tool.

[pfirmstone]

Is your feature request related to a problem? Please describe.

• Currently SecurityPolicyWriter builds a policy file and doesn't check for an existing policy file, however someone building a policy file may need to run different scenarios or users, and build the policy file.
• SecurityPolicyWriter duplicates grants where the same CodeSource is loaded into a different ClassLoader, as the policy file doesn't deal with ClassLoader instances, it would be helpful if duplicates were removed.

Describe the solution you'd like Avoid duplicate grants when running a JVM process more than once, that uses the same policy file.

Describe alternatives you've considered No alternatives considered.

[pfirmstone]

Add a properties file option, to be included in policy files for later property expansion, for file paths.