Cleans up issues across a few modules

Enables warnings on ui-text, ui-test, ...:ui-material-studies,
...:ui-material-demos and fixes issues that break as a result

Fixes every @Children usage to properly specify @Composable, this
is needed to prevent compiler warnings.

Fixes some incorrect package names in text/src/androidTest

Also renames ui-material-studies folder to material-studies to match
material-demos

Bug: b/131745428
Bug: b/130787808
Test: ./gradlew compileDebugKotlin && ./gradlew
compileDebugAndroidTestKotlin

Change-Id: Ib70af30acde7440afb59130e0dddb5a463516cbe

diff --git a/ui/text/src/androidTest/java/androidx/ui/engine/text/platform/ParagraphAndroidTest.kt b/ui/text/src/androidTest/java/androidx/ui/engine/text/platform/ParagraphAndroidTest.kt
index 4f192d4..1f3189d 100644
--- a/ui/text/src/androidTest/java/androidx/ui/engine/text/platform/ParagraphAndroidTest.kt
+++ b/ui/text/src/androidTest/java/androidx/ui/engine/text/platform/ParagraphAndroidTest.kt

@@ -1,4 +1,4 @@
-package androidx.ui.port.engine.text.platform
+package androidx.ui.engine.text.platform
 
 import android.graphics.Paint
 import android.text.TextPaint
@@ -26,25 +26,23 @@
 import androidx.ui.engine.text.BaselineShift
 import androidx.ui.engine.text.FontStyle
 import androidx.ui.engine.text.FontSynthesis
+import androidx.ui.engine.text.FontTestData.Companion.BASIC_MEASURE_FONT
 import androidx.ui.engine.text.FontWeight
 import androidx.ui.engine.text.ParagraphBuilder
 import androidx.ui.engine.text.ParagraphStyle
 import androidx.ui.engine.text.TextAlign
 import androidx.ui.engine.text.TextDecoration
+import androidx.ui.engine.text.TextGeometricTransform
+import androidx.ui.engine.text.TextIndent
 import androidx.ui.engine.text.TextStyle
 import androidx.ui.engine.text.font.FontFamily
 import androidx.ui.engine.text.font.asFontFamily
-import androidx.ui.engine.text.platform.ParagraphAndroid
-import androidx.ui.engine.text.platform.TypefaceAdapter
 import androidx.ui.engine.window.Locale
-import androidx.ui.painting.Color
-import androidx.ui.engine.text.FontTestData.Companion.BASIC_MEASURE_FONT
-import androidx.ui.engine.text.TextGeometricTransform
-import androidx.ui.engine.text.TextIndent
 import androidx.ui.matchers.equalToBitmap
 import androidx.ui.matchers.hasSpan
 import androidx.ui.matchers.hasSpanOnTop
 import androidx.ui.matchers.notHasSpan
+import androidx.ui.painting.Color
 import androidx.ui.painting.Shadow
 import com.nhaarman.mockitokotlin2.any
 import com.nhaarman.mockitokotlin2.eq