Backported embedded API from master.

[siepkes]

Adds new classes to hold parameters of operations on the directory server: ConnectionParameters, ImportParameters, RebuildIndexParameters, ReplicationParameters, SetupParameters, UpgradeParameters.

[Kortanul]

@siepkes Are you sure this is the target branch you wanted for this operation? Or is this PR supposed to target master after master is changed to be based off of 3.5 instead of 4.x?

I ask because:

• I was thinking that we weren't back-porting features from master to 3.5; I thought we were going to create a new 4.x from 3.5 then port features from the old 4.x to that new 4.x codebase.
• CI failed because the versions did not match (parent POM was missing).

[siepkes]

@Kortanul The branch is indeed not the right one. I made the PR against this branch because it needed to be on something 3.5-ish and not master. I just put it here so people could build a DS required for an AM 14 build. I should have made that clearer, sorry about that.

So this needs to go in the new 4.x branch as you said: Create a new 4.x from 3.5 then port features from the old 4.x to that new 4.x codebase.