wallet: avoid display the long file name on txs

[garyyu]

Minor improvement on wallet txs display.

Before this PR:

$ grin wallet txs
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Id  Type        Shared Transaction Id                 Creation Time        Confirmed?  Confirmation Time    Num.    Num.     Amount    Amount   Fee    Net         Tx  
                                                                                                             Inputs  Outputs  Credited  Debited         Difference  Data 
================================================================================================================================================================================================================
 0   Confirmed   None                                  2019-01-19 13:38:50  true        2019-01-19 13:38:50  0       1        60.018    0.0      None   60.018      None 
     Coinbase                                                                                                                                                        
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 1   Sent Tx     43955493-2648-488b-a4fd-1a4e775d1c54  2019-01-21 03:21:43  true        2019-01-21 03:26:24  1       1        59.01     60.018   0.008  -1.008      43955493-2648-488b-a4fd-1a4e775d1c54.grintx 
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

The TxData filename is using the Shared Transaction Id as the name and with fixed extension .grintx. So, perhaps we can just display Yes/None for the TxData status instead of a long filename, to avoid the wrapped lines on laptop screen.

After this PR:

$ grin wallet txs
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Id  Type        Shared Transaction Id                 Creation Time        Confirmed?  Confirmation Time    Num.    Num.     Amount    Amount   Fee    Net         Tx  
                                                                                                             Inputs  Outputs  Credited  Debited         Difference  Data 
=========================================================================================================================================================================
 0   Confirmed   None                                  2019-01-19 13:38:50  true        2019-01-19 13:38:50  0       1        60.018    0.0      None   60.018      None 
     Coinbase                                                                                                                                                        
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 1   Sent Tx     43955493-2648-488b-a4fd-1a4e775d1c54  2019-01-21 03:21:43  true        2019-01-21 03:26:24  1       1        59.01     60.018   0.008  -1.008      Yes 
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

[yeastplume]

Yep, think that's fine