Should disable COMPOSE menu item

When message viewing and tap the next icon, menu icons (previous, next, delete and replys) disappears for an instant.
But a compose icon remains, then tap it accidentally.
Enable AOSP builds
Build with SDK 19
Add support for KitKat's Storage Access Framework

This allows users on KitKat to add multiple attachments at once.
Fix 'endless' loop in ImapFolderPusher

Under certain circumstances it's possible that the 'push state' isn't
updated to contain the most recent 'UIDNEXT' value. In that case
ImapFolderPusher.start() would execute the same code path through its
main loop over and over again, preventing the device from going to
sleep.
Rather than changing the code to update the 'push state' in the corner
case that triggers the behavior described above, this commit introduces
another mechanism to track the 'UIDNEXT' value. This should also catch
as of yet unknown cases where the 'push state' isn't properly updated.

At some point in the future I hope we get to a point where we only
persist the 'push state' when we manually stop/restart the service.
During normal operation there's no need to read from/write to storage
all the time.

Fixes issue 4907
Remove old setting for message content font size

- export new setting
- add upgrade code to convert old setting to new format
Update changelog for 4.901
Extract code to scale the slider value for the message content font setting
Bumped manifest to 4.901
Fix version codes in changelog
removed unread field mAccount
removed unnecessary unboxing followed by reboxing

Since id is a Long, Long.valueOf(long) unboxed the Long to a primitive
long, then reboxed it into a Long instance, which was again unboxed to
allow it to be set as an element of the array of longs. This commit
reduces the number of boxings from 3 to 1.
Use more efficient entrySet iterator instead of keySet + get()

The loop extracted keys from `folderMap` and then called
`folderMap.get(...)` for every key. If both the key and the value needs
to be iterated on, `Map.entrySet()` is a more efficient solution as it
doesn't require O(n) Map lookups.
typofix in comment (desti{o,}nation)
replaced unnecessary explicit iterator use with for-each loop
replaced unnecessary explicit iterator use with for-each loop
removed unnecessary explicit cast
replaced for with for-each loop and optimized List implementation
use built-in TextUtils.join instead of StringBuilder
converted for to for-each loop with short circuit evaluation