RFC: Work around null commit when updating submodules

Bug: Issue 2498
Change-Id: I5d82ead765bc743d3392a1333cd2c3fc4cf971c7
Fix: Label update operation is executed as insert

When updating an existing label value with command like

 ssh -p 29418 user@review gerrit review <change>,<patchset> --label code-review=+1

where the lower case label name will make the update operation
become insert operation.  This causes an exception:

  "Unique index or primary key violation"

Use standard label name instead of lower case name.

Bug: Issue 2515
Change-Id: I735a5f84d0569554c050b60b8984ee83aa941d39
Another attempt to fix submit rule evaluation for non blocking labels

New change screen changed the logic for submit status evaluation
by moving it partially to the client side.  The change can be submitted
only when all needed labels have max scores and there is no labels exist
with min score. The computation of rejection is based on `rejected`
attribute in LabelInfo class. This attribute was set in two places:

1. As outcome of submit rule evaluation (with blocking functions)
2. In setLabelScores() to render the result for non blocking labels

After overriding of rejected attribute for non blocking labels it was
not possible any more to differentiate on the client side if one
particular label was rejected for information purpose only or because
it was blocked.

5a32a6dc15b73d412645598648ac089eacf29b65 was trying to solve it by
not overriding the rejected attribute in setLabelScores(). The
consequence of doing it was however, that custom labels with min
score were rendered not as rejected but as disliked.

This change introduces the `blocking` attribute in LabelType class to
carry out the missing information to the client to perform the correct
submit status computation. Now the rejected attribute can be overridden
for custom non blocking labels and rendered correctly.

Bug: Issue 2453
Bug: Issue 2497
Change-Id: Ic5092342b0e2153eb43f5e06fda4fcac4699844e
Change dialog title from Error to Warning on intraline diff timeout

When the value of 'diff_intraline.timeout' is not long enough
to let IntraLineLoader compute the intraline, Gerrit will set its
status as TIMEOUT and cache it.  When the user opens the diff view
a dialog will appear with Error title to say "Intraline difference
not available due to timeout".

Change the 'Error' title to 'Warning' to reduce number of complaints
from users.

Change-Id: I440d03593eb82d9c6c213cdc77d3fd3d50a760eb
Update 2.8.2 release notes with recently merged changes.

Change-Id: Id8b008abd7d3a01f23fe61370612c681183c8605
Merge "RFC: Work around null commit when updating submodules" into stable-2.8