Added the search part
Do not know what
Revert "Do not know what"

This reverts commit 49457c6c663d40e592164b39867c33aed99f509b.
Private logic constructor, add ,sort by end date

and unit test for add
remove unused CommandEdit.java
search
some change about logic and search
Made search work

1. Modified processSearch method in Interpreter
2. Modified executeSearch method in Logic
3. Modified execute method in Logic
Make some change in logic and storage
Revert "Make some change in logic and storage"

This reverts commit 67b4c052944cff3273c610f1eea87ca452afa2f5.
unit test

1. transfer cmdSearch to logic
2. unit test for search
3. unit test for ValidationCheckTest
4. remove unused commandSearch.java
make some change on logic and storage
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/Logic.java
	src/ValidationCheckTest.java
recommit
implemented new edit
removed some unnecessary displays
some change of storage
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/Logic.java
	src/ToDoManagerUnitTests.java
Merge remote-tracking branch 'origin/Qingtao_Add/Delete/Undo'