Parser change to singleton, create more private methods
Parser change to singleton
Merge branch 'master' into xjy-parser
Merge remote-tracking branch 'origin/xjy-parser' into sun-defcoding
temporary integration with singleton parser
parser logger and asserted
Merge remote-tracking branch 'origin/hyungjon-data' into sun-defcoding
Merge remote-tracking branch 'origin/hyungjon-data' into sun-defcoding

Conflicts:
	src/application/Controller.java
Command class renamed as CommandInfo class, date and time formatted
Merge branch 'xjy-parser' of https://github.com/cs2103aug2014-w14-2j/main into hyungjon-data

Conflicts:
	src/application/Controller.java
enabled undo function, for Controller, DataStorage and TaskManager