updates for parser
changed enum for Done in accordance with CommandFilter change
Logging done for StorageDatabase, requires LOGGING_MODE_ON to be set to true, after that, errors will be logged in format
TIME:
FUNCTION:
ERROR:

into a txt file
Logging done for StorageExecutor, requires LOGGING_MODE_ON to be set to true, after that, errors will be logged in format
TIME:
FUNCTION:
ERROR:

into a txt file
Some refactoring to remove magic numbers with variables
Merge branch 'master' of https://github.com/cs2103aug2014-t14-4c/main into mybranch