Merge remote-tracking branch 'origin/master'
[FIXED JENKINS-7291] Permit flyweight tasks to run on master even when it has zero configured executors.

Always adding Computer for master as a fallback

The original proposed fix for JENKINS-7291 creates a Computer object
transitively. This seems unwise as it violates the design of Computer
as stated in the javadoc, and for example we can end up creating two
Computers for the master.

I think a better fix is to create a Computer for the master all the
time, even if there's no executors configured. The discrimination in
Queue.makeBuildable would ensure that such phantom Computer is only used
as a last resort (statistically speaking).

I've also tweaked executors.jelly a bit. I simplified it somewhat
based on the idea that "if there's only one computer to show, the
context is likely making it obvious".

(I must be missing the intricacy in the current code.)

Originally developed in a branch at
2c5b57fcc1f39ed39057254e802f4183db5aa0dc then squashed for clarity.
Accidental Java 7 dependency in test.
[FIXED JENKINS-3265] Hotfix for regression in matrix project loading from 25084f5.(cherry picked from commit 3370e6edf5e0e7c7a8cf22e4a7a5decc24c45205)
[JENKINS-17337] Added test for NPE.(cherry picked from commit 1bf958afb196d0c56b37f00681027a549d0c9189)
recording the fix
creating an RC branch
Revert "[JENKINS-17337] Added test for NPE.(cherry picked from commit 1bf958afb196d0c56b37f00681027a549d0c9189)"

This reverts commit 18b5f4f13377349b1c249c2f62d11966c5b7dd9d.
It looks like this change depends on other test harness related changes.
It doesn't build on this branch.
[maven-release-plugin] prepare release jenkins-1.508
[maven-release-plugin] prepare for next development iteration
updated changelog for release
updated changelog as a part of the release
merged back the RC branch

Conflicts:
	changelog.html
1.509 RC inherits from 1.508
Trunk is toward 1.510
Replace \r\n with system property line.separator

Implementing change as suggested by vjuranek
Merge branch 'master' into JENKINS-16942
Restored some orphaned translations.
Orphaned messages file.
confirmDelete (and confirmDeleteAll) already say why a build cannot be deleted (and prevent you from proceeding), so no need to hide the Delete link in this case.