added new test case for search and editted RestoreTest
added basic javadoc

missing description about the purpose of the method
finished javadoc for command package
added javadoc for recurrence, taskID, tasktype, time, title
added javadoc for classes

Complete, DeleteOption, Description, Keyword, Location
added javadoc for CommandType, Option, ParameterList
added testcases

added more assertion checks for
- CommandTypeTest
- CompleteTest
- DescriptionTest

Added new testfile:
- DeleteOptionTest
updated testcases

added extra assertion tests for:
- TaskIDTest
- ParameterListTest
- KeywordTest
edited javadoc
updated testcases and added assertion tests
Merge remote-tracking branch 'main/chunhui'