weblogic-certificate plugin

Initial version of the weblogic-certificate plugin

Introduces 2 new Containers:
- CustomTrustKeyStore
- CustomIdentityKeyStore

and 2 Deployables
- TrustCertificateSpec
- IdentityCertificateSpec

and an SSL Channel restart contributor
> I think it should, but we should fix this in the WLS plugin (wls/runtime/base.py)

I agree. But would it not make sense to _also_ fix it here and not repeat the same problem that exists in base.py?