ACCUMULO-3217 Make KeyValue extend SimpleImmutableEntry instead of implement Map.Entry.

We get toString, hashCode and equals for free by extending SimpleImmutableEntry
over implementing Map.Entry. Without this change, users couldn't properly
use the Entry<Key,Value> objects that were returned by Scanners and BatchScanners.
Merge branch '1.5' into 1.6

Conflicts:
	server/tserver/src/main/java/org/apache/accumulo/tserver/Tablet.java
Merge branch '1.6'

Conflicts:
	core/src/main/java/org/apache/accumulo/core/data/Key.java
	core/src/main/java/org/apache/accumulo/core/data/KeyValue.java
	server/tserver/src/main/java/org/apache/accumulo/tserver/TabletServer.java
	server/tserver/src/main/java/org/apache/accumulo/tserver/tablet/Tablet.java
ACCUMULO-3215 Ensure that ImportTable writes absolute paths, not relative.

ImportExportIT creates a table, exports it and then imports it to the
same instance to ensure that the imported copy is equivalent
to the original. Without the changes to ImportTable, the test failed
because the copy was unusable due to incorrect metadata table entries.
Merge branch '1.6'

Conflicts:
	server/master/src/main/java/org/apache/accumulo/master/tableOps/ImportTable.java
ACCUMULO-3217 Fix use of deprecated members
Merge branch '1.6'
ACCUMULO-3220 Fail fast if the provided cipher isn't a block cipher.
Merge branch '1.6'
ACCUMULO-3221 Ensure arithmetic happens as longs and not integers.
Merge branch '1.5' into 1.6

Conflicts:
	core/src/main/java/org/apache/accumulo/core/util/shell/Shell.java
Merge branch '1.6'
ACCUMULO-3220 Make sure to re-set the local cipher variable when it wasn't initialized
Merge branch '1.6'
ACCUMULO-3215 Remove deprecated javadoc link

  Remove unneeded javadoc link to deprecated property in a test to avoid a
  deprecation warning.
Merge branch '1.6'
ACCUMULO-3222 Get Durability for tablet after null check. Add final modifiers.
ACCUMULO-3218 Set the list separator to \0 to 'disable' list interpretation

ZooKeeperInstance, because of how commons-configuration was parsing the
values, was treating a comma separated list of ZK servers (which
we intend to be a single value) as multiple and only returning
the first when getString was called on its key. We have no case
where we actually want values to be automatically parsed into an
array, so we can set it to a separator highly unlikely to be used.
ACCUMULO-3223 Explicitly handle null from getOnlineTabletsForTable
Merge branch '1.6'

Conflicts:
	core/src/test/java/org/apache/accumulo/core/client/ZooKeeperInstanceTest.java