Follow-up fixes for scheduled-transfer implementation.

related !374 (merged)

Closes: #206 (closed)

This MR includes fixes for:

1. Fixed issue to display only the next 10 upcoming scheduled transfers.
2. Fixed calculation of amount of upcoming scheduled transfers.
3. Fixed typo send -> sent in help message of clive process transfer-schedule,
4. Fixed bug that requires from user passing pair_id even when there was only one transfer to receiver,
5. Fixed bug that prevents from removing scheduled transfer when there was only 1 execution left,
6. Remove Memo column from upcoming table,
7. Adjust time format of Next column in upcoming table,
8. Add information in help of clive show transfer-schedule modify about first execution after changing value of frequency.