updates:
- changed location character to '@'
- changed escape sequence to inverted commas
- allowed index range for delete in 2 formats (f1, f2 and f1-f5)
- allow flexible update by field - return commandAdd obj hasMissingArgs,
but with arguments intact, null/empty arraylist for unspecified fields
Merge branch 'UI'
update gui
edit visuals
default view agenda in GUI