Update viewCommand to accept more flags and arguments, and fixed multiple bugs (v0.2)

[e0958902]

Checklist for feature implementation and modification

Closes #162, #175, #171, #169, #165, #153, #152, #166, #181

• [x] Added relevant milestone (under milestone tab on the right)
• Implementation
  • [x] Sources (if any) credited under both relevant section(s) and Developer Guide (Acknowledgement)
  • [ ] JUnit Test(s)
• Documentation
  • [x] JavaDoc for classes and methods
  • Developer Guide
  • [ ] Design (Can add as a todo statement for later on)
  • [ ] Implementation (Can add as a todo statement for later on)
  • [ ] Relevant User Story present
  • [ ] Non-functional requirement(s) that the feature addresses (if any)
  • [ ] Glossary of the (technical) term(s) used (if any)
  • [ ] Specialised instructions for manual testing (if any)
  • User Guide
  • [x] Description and usage of feature (if any)
  • Contributions (under /docs/team/*.md)
  • [x] Code/Feature/Enhancement contribution
  • [ ] Developer Guide contribution
  • [x] User Guide contribution
  • [x] Misc and team-based admin tasks (if any)

Checklist for non-implementation related PR

Closes #162, #175, #171, #169, #165, #153, #152, #166, #181

• [x] Added relevant milestone (under milestone tab on the right)
• Documentation (Contributions)
  • [ ] Developer Guide contributions (if any)
  • [x] User Guide contributions (if any)
  • [ ] Review contributions (if any)
  • [ ] Miscellaneous and team-based admin tasks (if any)

Additional Information

The flags will filter out the medications according to their flag type;

Current version only supports "view -l "

In v0.2, 2 and 3 will be implemented to include comparator and sorted according to expiry date and quantity respectively.

1. [x] view -n <------- Shows medications that contains the name
2. [x] view -q <-- Shows medications that have that quantity lower than specified
3. [x] view -e <------ Shows medications that will expire by specified year
4. [x] view -r <----Shows medications that contains the specified remarks
5. [x] view -r -e Throws an error message that you can only use one flag