Front-port of r10103,10105,10113.

Increased encapsulation of ReplicationDomain.IEContext + moved more behaviour to it.
Reduced members' visibilities in LDAPReplicationDomain + removed several methods.


ReplicationDomain.java:
Do not access the IEContext field several times in one method in case it gets updated in the middle, instead accessed it once at the top of a method and passed it down private method calls.
Moved importInProgress(), getTotalEntryCount(), getLeftEntryCount() to IEContext class.
Added getImportExportContext().
Made ieContext private and used an AtomicReference for it + In acquireIEContext() and releaseIEContext(), removed now useless synchronized keyword.
In acquireIEContext(), returned the created IEContext + changed all client code to assign a variable from the result.

LDAPReplicationDomain.java:
Reduced visibility of many methods.
Removed followImport field + setFollowImport() which can be calculated from importErrorMessageId + added and used isFollowImport() instead.
Replaced calls to "retrievesBackend(getBaseDN())" with getBackend() + inlined retrievesBackend().
Called getImportExportContext() to access the IEContext.

FractionalLDIFImportPlugin.java:
Consequence of removing LDAPReplicationDomain.setFollowImport().
In doLDIFImport(), factorized code between branches of an if statement + extracted method isNotEmpty().
In flushFractionalConfigIntoEntry(), used StaticUtils.collectionToString() + extracted method add()

ReplicationMonitor.java:
In getMonitorData(), simplified the code.

ReplicationDomainTest.java:
Extracted methods waitEndExport(), assertExportSucessful(), buildExportedData().
Called ReplicationDomain.getImportExportContext().