Add theme version checking

Add a themeversion value to the ui.xml details section. Check this
value against a define during early theme loading. If we are
loading a custom theme, then reject the custom theme if the
version does not match (or not defined) and load the stock theme.
If it is the stock theme, show a warning but continue loading.

Also fix an issue with changing overlays. Not sure how it ever
worked before, but it works now.

TLDR: Use the stock theme if the custom theme version does not
match.

Change-Id: I0277cbe035cbec7e16b6327500762dadf9c1c5c8
diff --git a/gui/theme/common/languages/en.xml b/gui/theme/common/languages/en.xml
index c77d3a2..47c7e76 100755
--- a/gui/theme/common/languages/en.xml
+++ b/gui/theme/common/languages/en.xml
@@ -667,5 +667,6 @@
 		<string name="no_real_sdcard">This device does not have a real SD Card! Aborting!</string>
 		<string name="cancel_sideload">Cancelling ADB sideload...</string>
 		<string name="change_fs_err">Error changing file system.</string>
+		<string name="theme_ver_err">Custom theme version does not match TWRP version. Using stock theme.</string>
 	</resources>
 </language>
diff --git a/gui/theme/landscape_hdpi/ui.xml b/gui/theme/landscape_hdpi/ui.xml
index c3bb96f..73ccdf1 100644
--- a/gui/theme/landscape_hdpi/ui.xml
+++ b/gui/theme/landscape_hdpi/ui.xml
@@ -6,6 +6,7 @@
 		<title>Backup Naowz</title>
 		<description>Default basic theme</description>
 		<preview>preview.jpg</preview>
+		<themeversion>1</themeversion>
 	</details>
 
 	<include>
diff --git a/gui/theme/landscape_mdpi/ui.xml b/gui/theme/landscape_mdpi/ui.xml
index ae40683..293742e 100644
--- a/gui/theme/landscape_mdpi/ui.xml
+++ b/gui/theme/landscape_mdpi/ui.xml
@@ -6,6 +6,7 @@
 		<title>Backup Naowz</title>
 		<description>Default basic theme</description>
 		<preview>preview.jpg</preview>
+		<themeversion>1</themeversion>
 	</details>
 
 	<include>
diff --git a/gui/theme/portrait_hdpi/ui.xml b/gui/theme/portrait_hdpi/ui.xml
index cb92b9f..917e93b 100644
--- a/gui/theme/portrait_hdpi/ui.xml
+++ b/gui/theme/portrait_hdpi/ui.xml
@@ -6,6 +6,7 @@
 		<title>Backup Naowz</title>
 		<description>Default basic theme</description>
 		<preview>preview.jpg</preview>
+		<themeversion>1</themeversion>
 	</details>
 
 	<include>
diff --git a/gui/theme/portrait_mdpi/ui.xml b/gui/theme/portrait_mdpi/ui.xml
index 450860e..19f199e 100644
--- a/gui/theme/portrait_mdpi/ui.xml
+++ b/gui/theme/portrait_mdpi/ui.xml
@@ -6,6 +6,7 @@
 		<title>Backup Naowz</title>
 		<description>Default basic theme</description>
 		<preview>preview.jpg</preview>
+		<themeversion>1</themeversion>
 	</details>
 
 	<include>
diff --git a/gui/theme/watch_mdpi/ui.xml b/gui/theme/watch_mdpi/ui.xml
index 4e4cc1f..163a82b 100644
--- a/gui/theme/watch_mdpi/ui.xml
+++ b/gui/theme/watch_mdpi/ui.xml
@@ -7,6 +7,7 @@
 		<title>Backup Naowz</title>
 		<description>Default basic theme</description>
 		<preview>preview.jpg</preview>
+		<themeversion>1</themeversion>
 	</details>
 
 	<include>