Capitalisation according to Android guidelines

Not all updated capitalisations were correct.
Merge pull request #1554 from thoughtbox/patch-8

Capitalisation according to Android guidelines
Include gradle-witness plugin for verifying dependencies.
No need to verify a local module.

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Added APN Settings for T-Mobile UK
Fixes #1558
Merge pull request #1573 from Jabro/master

Added APN Settings for T-Mobile UK
Upgrade android plugin to stay compatible with latest Android Studio

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Merge pull request #1581 from mcginty/android-studio-060

Upgrade android plugin to stay compatible with latest Android Studio
Fixing a typo in the WhisperPush error message
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Merge pull request #1589 from jlund/cyanogen-error-message

Fixing a typo in the WhisperPush error message
Use ACTION_OPEN_DOCUMENT for Android >= KitKat.

Fixes #926.

We have to do this, since with the new Storage Access Framework,
otherwise we can open the Uri only *once*. This would work well
unless someone saves a draft and goes back to the conversation -
then the Uri is opened again without the required permissions.

See:

https://developer.android.com/guide/topics/providers/document-provider.html#client

...for details.
Cache circle cropped photos on Recipient.
Add correct contextual menu options on 'Send' button.

[Send TextSecure message | Send unencrypted SMS | Send encrypted SMS]

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Move media attachment long-click event to context menu.

Long-click on a media attachment will now bring up the normal
context menu for a ConversationItem long-click, but with the
addition of a "save attachment" option.

This allows users to long-click on messages with media in them
and still see the other contextual menu options.

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Clear search when opening the drawer

Before this change opening the drawer while a filter was active
would hide the search bar but keep the conversation list filtered,
so there was no indication of an active filter.
Allow passphrase unlock from "unlock" keyboard action.
Use "date sent" as timestamp for push, "date received" for SMS.

The "sent time" is not reliable on SMS messages.  This switches
to using "sent time" by default for push messages, but "received
time" for SMS messages.
Reword the very confusing screen security setting
reorganize readme

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Better share intent handling.

1) Guess mime type from share intent EXTRA_STREAM uri.

2) Always include EXTRA_TEXT (if present)