* CORDA-3471: Create `CordaTransactionSupport` and use wherever possible instead of `CordaPersistence`
* CORDA-3471: Address comments by @mnesbit
- Relocate `CordaTransactionSupport` to `core`
- Create a lighter version of transaction - `VaultTransaction` that gives access to `session` object only.
* CORDA-3471: More changes after discussion with @mnesbit
- Rename `VaultTransaction` into `SessionScope`.
* CORDA-3471: Revert changes to most of the files after conversation with @mnesbit and @rick-r3
* CORDA-3471: Introduce `CordaTransactionSupportImpl` and make it accessible via `AppServiceHub`.
* CORDA-3471: Minor change (comment).
* CORDA-3471: Address input from @mnesbit
* CORDA-3471: Address input from @rick-r3
* CORDA-3471: Make Detekt happier
* CORDA-3471: Add a new test that proves transactions can be started from client threads
As requested by @mnesbit
* CORDA-3471: Change log and documentation update.
As requested by @mnesbit
