email: prevent stock email app to unset firstSnippet on mark/unmark as read

If the email conversation only have one message then firstSnippet is the only valid
snippet in the converation item. Multiple conversation items are only supported by Gmail
which call the "set" method to set those snippets. This changes prevents to set
firstSnippet = null when user mark/unmark the item as read in stock email app.

Change-Id: I85f2ff0ab212c2a64450c3d46323418b9340fe40
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Automatic translation import

Change-Id: I04e17aa4be7f44938e2563902f85eceee563a575
unifiedemail: display a "load more" button

If the message is partial loaded, then show a "load more" button instead of an attachment
bar. A partial message doesn't implies that the message contains attachments or that
all attachment were loaded.

Require http://review.cyanogenmod.org/#/c/67523/

Change-Id: I8998ac7f7c46d7e6698ee471fb89185504d1ecf0
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
UnifiedEmail: Update "Fetching message" string

Change-Id: I8dbcf85280978e7b65f7f09584791a4f6678e60f
Automatic translation import

Change-Id: Ifa6b3c70f4711424b8375ee806d1a3a682d9ec7e