Change current deck on drop-down deck change.
Improvements to the write answer feature:
* Hide the "......" prompt when write answer is off
* Show only the correct answer when nothing is typed, including in the write answer off case
* Show the correct answer normally instead of marked green when write answer is off.
* Add class typeOff when write answer is off, to allow hiding the correct answer via CSS.
Playing sound files specified by absolute URI was implemented.
Fix for issue 2073.  Get rid of the swap button and swapText() function.
Prepare error report when null encountered in queryColumn
Scroll the deck list to the currently selected deck and center it

On tablets, the currently selected deck is highlighted in the deck list. If there are many decks, then the selected deck may not be initially visible. This change will scroll the decklist to ensure AnkiDroid always opens up on tablets with the currently selected deck visible.
Synchronous prepare() was replaced with prepareAsync().
Static field was renamed according to the code conventions.
Typo fixed.
Added missed 'break' instruction.
null-dereference possibility was eliminated.
'==' strings comparison is replaced with call to 'equals()'.
Redundant null-checks were removed.
Pass to the Math.round() double value rather than integer.
Integer values boxing was removed.
Unnecessary casts and unused variables were removed.
Unnecessary boxing and unboxing were removed.
Redundant toString() removed.
Manual array to collection copy replaced with addAll.
The manual copying of array contents replaced by call to System.arraycopy()