Admin: Improve Bots page, add columns

[harsh-jindal]

Fixes #2873

Changes: Added Defualt Skills and Bot Sites column.

Demo Link: https://pr-2794-fossasia-susi-web-chat.surge.sh

Screenshots of the change: [Add screenshots depicting the changes.]

[harsh-jindal]

Drafts tab shall be added after this is merged fossasia/susi_server#1362

[harsh-jindal]

Draft API not fetching all the drafts. Opened an issue for the same here: fossasia/susi_server#1364

[mariobehling]

• Under Actions "View" only shows the page with the draft name, but no other bots info. It only shows the standard info.
  
• Author of bot is missing

[harsh-jindal]

@mariobehling Getting the author name and showing the info on clicking on view option depends on getting the emailID from the server but while storing a new bot we only store the uuid of the user. I had asked on the gitter channel if there is some way to get emailId from uuid here: https://gitter.im/fossasia/susi_server?at=5d48329041d5cd61b5bade43

[akshatnitd]

Research on how it can be done, rather than waiting to someone to do it for you. I am sure, this is being used somewhere in the codebase. Search the codebase properly.

[harsh-jindal]

@akshatnitd I have researched on it. Uuid is formed from encoding the user's email. It's a one way encoding. So IMO we shall save the users email while creating a new bot. But then for old bots the view and modify will not work.
Please suggest other ways. Maybe I can try looping through all the authorized clients and check whether they have bots and display. Shall I go ahead this way ?

[akshatnitd]

Create a separate issue for the missing field and finalise this PR.

[harsh-jindal]

@akshatnitd Made the changes. Please review.
Note: Only additions of columns is done in this PR.
View option needs to fixed on the server as said in previous comments we need email Id from uuid for that.