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
> It should be part of the standard WLS plugin imho

I'm not disagreeing, but that's a separate discussion ;-) But while that is _not_ the case, could we use a different name to avoid confusing users and triggering support requests talking about "this wls.CustomKeyStore problem that I don't understand..."?