Add sessions to sidebar and show filter and export options

[mariobehling]

Enhance presentation of the schedule as follows:

1. Implement a link "Sessions" below the "Schedule" in the sidebar and show the schedule page same as on talk. On the schedule page also show the filter and export options.
   

2. Show the filter and export options on the schedule
   

[Yashkrit-Singh]

@mariobehling can you help me regarding setting up this project locally? I am facing issues with that. I think i can fix this issue