Add Student Projects to "GCI 19 Projects" repository and Delete non-Open Source projects

After GCI we often see that links are outdated and projects get deleted. In order to keep things aligned, please add a copy of listed student projects to the repository at https://gitlab.com/fossasia/gci19-projects and link them.

Also export any Google doc and host it on Gitlab.

It seems that also projects were added that are not Open Source and related to GCI, e.g. the track-app. Please take out non-Open Source and GCI related apps from the website.