let users click on the timetable to select slots

**Is your feature request related to a problem? Please describe.**
When selecting of slots can be done just by clicking on slots on the time table, why give out buttons? I get its asthetically pleasing, but we can either:
1. let that go
2. Allow users to select and deselect slots both ways

**Describe the solution you'd like**
Why not just allow user to click on the time table to select labs, theory slots, and grey out slots there only

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**

Start by running the application and locating the timetable UI and existing slot-selection behavior. Check how lab and theory slots are selected, deselected, and greyed out; done means users can perform those actions directly on timetable slots as well as through the existing controls, without breaking clash handling.

Written by the indexing model from the issue text.