Add README files to top-level and update the project ones

4 files changed, 70 insertions, 5 deletions

diff --git a/README.md b/README.md
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+# GNU Taler Android Code Repository
+
+This git repository contains code for GNU Taler Android apps and libraries.
+The official location is: 
+
+    https://git.taler.net/taler-android.git
+    
+## Structure
+
+* [**anastasis-ui**](/anastasis-ui) - an Android library for sync and backup UI.
+  See [Anastasis](https://docs.taler.net/anastasis.html).
+* [**cashier**](/cashier) - an Android app that enables you to take cash and give out electronic cash
+* [**merchant-lib**](/merchant-lib) - a library providing communication with a merchant backend
+  to be used by the point of sale app below.
+* [**merchant-terminal**](/merchant-terminal) - a merchant point of sale terminal Android app
+  that allows sellers to
+  process customers’ orders by adding or removing products,
+  calculate the amount owed by the customer
+  and let the customer make a Taler payment via QR code or NFC.
+* [**taler-kotlin-android**](/taler-kotlin-android) - an Android library containing common code
+  needed by more than one Taler Android app.
+* [**multiplatform**](/multiplatform) - multi-platform Taler libraries
+  included as a [git submodule](https://git-scm.com/docs/git-submodule)
+  from [`https://git.taler.net/wallet-kotlin.git`](https://git.taler.net/wallet-kotlin.git/)
+* [**wallet**](/wallet) - a GNU Taler wallet Android app
+
+## Building
+
+Before building anything, you should initialize and update the submodules by running
+    
+    $ ./bootstrap
+    
+Then, you can get a list of possible build tasks like this:
+    
+    $ ./gradlew tasks
+    
+See the [Taler developer manual](https://docs.taler.net/developers-manual.html#build-apps-from-source).
+for more information about building individual apps.
diff --git a/cashier/README.md b/cashier/README.md
index e884f25..4382125 100644
--- a/cashier/README.md
+++ b/cashier/README.md
@@ -5,6 +5,10 @@ The purpose of this app is to enable people (a cashier) to take cash and give ou
 ## Building
 
 You can import the project into Android Studio
-or build it with Gradle on the command line:
+or build it with Gradle on the command line (from the repository root):
 
-    $ ./gradlew build
+    $ ./bootstrap
+    $ ./gradlew :cashier:build
+
+More information can be found in the
+[Taler developer manual](https://docs.taler.net/developers-manual.html#build-apps-from-source).
diff --git a/merchant-terminal/README.md b/merchant-terminal/README.md
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+++ b/merchant-terminal/README.md
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+# GNU Taler Point of Sale merchant terminal
+
+This merchant point of sale terminal Android app allows sellers to
+
+* process customers’ orders by adding or removing products,
+* calculate the amount owed by the customer and
+* let the customer make a Taler payment via QR code or NFC.
+
+## Building
+
+You can import the project into Android Studio
+or build it with Gradle on the command line (from the repository root):
+
+    $ ./bootstrap
+    $ ./gradlew :merchant-terminal:build
+
+More information can be found in the
+[Taler developer manual](https://docs.taler.net/developers-manual.html#build-apps-from-source).
diff --git a/wallet/README.md b/wallet/README.md
index 22e283f..32e2139 100644
--- a/wallet/README.md
+++ b/wallet/README.md
@@ -1,10 +1,15 @@
 # GNU Taler Wallet
 
 This package implements a GNU Taler wallet for Android.
-It is currently a UI for the wallet library writen in TypeScript.
+It is currently a UI for the
+[wallet library written in TypeScript](https://git.taler.net/wallet-core.git).
 
 ## Building
 
-It can be built with Gradle:
+It can be built from the project's main directory with Gradle:
 
-    $ ./gradlew build
+    $ ./bootstrap
+    $ ./gradlew :wallet:build
+
+More information can be found in the
+[Taler developer manual](https://docs.taler.net/developers-manual.html#build-apps-from-source).