vab support: merges and unmapping super devices

- check for merges before formatting data
- add advanced option for unmapping super devices

Change-Id: I38d4d3bbdfa071969016c3e000c86a4d03c71e45
diff --git a/twrpApex.cpp b/twrpApex.cpp
index 5531445..ca6cff4 100755
--- a/twrpApex.cpp
+++ b/twrpApex.cpp
@@ -185,3 +185,7 @@
 
 	return true;
 }
+
+bool twrpApex::Unmount() {
+	return (umount2(APEX_BASE, MNT_DETACH) == 0);
+}