add round letter avatar for contact w/o image
updating spash image
update LetterAvatar to better match Gmail material style
update links in README
update to latest appcompat_v7 (v21.0.3)
purge defunct XMPP cert pin for dukgo.com, the main COMODO one covers this

It seems that the dukgo.com certificate that included this signing cert has
been replaced by one that no longer is signed by this cert.  The new one is
signed by the higher level COMODO cert that is already included:

SubjectDN: CN=COMODO RSA Certification Authority, O=COMODO CA Limited, L=Salford, ST=Greater Manchester, C=GB
IssuerDN: CN=AddTrust External CA Root, OU=AddTrust External TTP Network, O=AddTrust AB, C=SE
Fingerprint: F5AD0BCC1AD56CD150725B1C866C30AD92EF21B0
SPKI Pin: 6E584E3375BD57F6D5421B1601C2D8C0F53A9F6E
make Orbot install link a direct link to app in Google Play and F-Droid

This market: URI syntax takes the user directly to the page for the app
itself, based on package ID, rather than doing a search.  This link also
works with F-Droid.

https://developer.android.com/distribute/tools/promote/linking.html
purge OtrContants, only a single value is used (helps with otr4j merge)
move OTRDATA TLV definitions to where the other TLVs are defined

This helps with the otr4j merge.  It shouldn't change the logic at all.
switch out custom bouncycastle repackage for spongycastle

https://rtyley.github.io/spongycastle/
spongycastle is a standard repackage of bouncycastle for Android:

The Android platform unfortunately ships with a cut-down version of Bouncy
Castle - as well as being crippled, it also makes installing an updated
version of the libraries difficult due to classloader conflicts.

Spongy Castle is the stock Bouncy Castle libraries with a couple of small
changes to make it work on Android:

* all package names have been moved from org.bouncycastle.* to
  org.spongycastle.* - to avoid classloader conflicts
* the Java Security API Provider name is now SC rather than BC
* no class names change, so the BouncyCastleProvider class remains Bouncy,
  not Spongy, but moves to the org.spongycastle.jce.provider package.
include languageButton in landscape layout

Fix a stupid mistake on my part, I added a new button to the regular layout
but not the landscape version of the layout.

java.lang.RuntimeException: Unable to start activity ComponentInfo{info.guardianproject.otr.app.im/info.guardianproject.otr.app.im.app.LockScreenActivity}: java.lang.NullPointerException
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
at android.app.ActivityThread.access$600(ActivityThread.java:123)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4424)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at info.guardianproject.otr.app.im.app.LockScreenActivity.onCreate(LockScreenActivity.java:96)
at android.app.Activity.performCreate(Activity.java:4492)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
... 11 more
sync up file layout with portrait version for easy comparing
fix crash when timer runs XmppConnection.handlePresenceChanged()

fixes #4276 https://dev.guardianproject.info/issues/4276

java.lang.NullPointerException
at info.guardianproject.otr.app.im.plugin.xmpp.XmppAddress.<init>(XmppAddress.java:26)
at info.guardianproject.otr.app.im.plugin.xmpp.XmppConnection.handlePresenceChanged(XmppConnection.java:2876)
at info.guardianproject.otr.app.im.plugin.xmpp.XmppConnection.access$2800(XmppConnection.java:130)
at info.guardianproject.otr.app.im.plugin.xmpp.XmppConnection$12.run(XmppConnection.java:3015)
at java.util.Timer$TimerImpl.run(Timer.java:284)