Perform an Import Async Task on Ok

After validation of DcData start importing data from the divecomputer using
DcImport Async Task. Appropriate changes made in other parts of the applications
such as
1. Appropriate strings for dialogs.
2. Cancel option interrupts the Import Task.
3. Cancel button is enabled or disabled on Import Task execution/completion.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>
Important changes to make sure the import works.

These changes include
1. Actual setup of native devdata by calling native functions.
2. Removing __android_log_print and replacing it with original vsprintf. Its
inclusion was causing SIEGSEGV.
3. Changes in DcData. Earlier, the methods were not making a lot of sense.

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>