Fixes issue with role election in cluster

Introduces tests and fixes for some edge cases that role election
 may come up against
Votes received that are actually delayed responses from a previous
 election could lead to wrong results. This is now guarded against
 by having versions marking elections and vote requests/responses
Election results could be reordered if one would fail to be
 broadcasted. Now this is guarded against by an election epoch, allowing
 election results to be ignored.
Instance and vote count could become wrong if an instance voted
 and then was marked as failed before the election finished. That could
 lead to cases where the role holder was not asked for a vote. Now,
 ElectionContext registers as a HeartbeatListener and will invalidate
 votes of instances that have failed.
This is added with backwards compatibility, so elections initiated by
 previous version instances will still go through and receive proper
 responses.
Fixes race that can cause duplicate writes in XaLogicalLog

There is a possible window where a transaction may fail to flush
 the log buffer (for example, during a commit) and even though
 it will set the KernelHealth to notOk, another thread can still
 come and try to flush the same contents again (say, by attempting
 a commit of its own tx). This can cause the log to be unrecoverable.
 This commit fixes this issue by introducing checks to KernelHealth
 before any write happens to the log's underlying file.
Merge pull request #2326 from digitalstain/1.9-fix-damaged-log-writes

Fixes race that can cause duplicate writes in XaLogicalLog
added script to detect unauthorized contributors
fix for TopPipe with duplicate values
Merge pull request #2332 from jexp/top-n-fix

fix for TopPipe with duplicate values
Merge pull request #2335 from nawroth/2.0-maint

Make sure old icons aren't used in the manual
Logging performance optimizations:
* Added custom Jetty logger that caches isDebugEnabled
* Changed LogbackService to cache isDebugEnabled
* Added isDebugEnabled check before toString() in HighPerformanceCache
Only add security filter if there are security rules
License header fix
Debug cache is now no longer static.
Added comment that the request log needs to decorate all other handlers.
Merge branch '1.9-maint' into 1.9-merge

Conflicts:
	community/kernel/src/main/java/org/neo4j/kernel/impl/transaction/xaframework/XaLogicalLog.java
	community/kernel/src/test/java/org/neo4j/kernel/impl/transaction/xaframework/XaLogicalLogTest.java
Added test for slave-only instance being elected coordinator
Fixes so that slave-only instances not only try not to win elections, but actively don't switch to master in the case they are coordinators (e.g. because the instance created the cluster)

Conflicts:
	enterprise/ha/src/main/java/org/neo4j/kernel/ha/HighlyAvailableGraphDatabase.java
	enterprise/ha/src/test/java/org/neo4j/ha/TestSlaveOnlyCluster.java
2.0.3 changelogs
Merge pull request #2339 from jakewins/1.9-merge

1.9 merge
Tagging for version 2.0.3
Handle pruning old format logs, Fixes #2265
Handle backup when no logs are present on target db.
Added +UNWIND+ to Cypher

UNWIND can be used to transform a collection into individual rows.