Add BitBucket webhook parser and statuses

[rick-nu]

What

• Adds a /webhook/bitbucket webhook target
• Parses BitBucket webhooks to statuses
• Added BitBucket to the documentation

Why

Since we're using BitBucket for one of our clients, we wanted to get some insights in BitBucket projects too. So we've recorded some webhooks and created a parser for it.

To do

• Add BitBucket webhook documentation
• Create repo:push parser
• Create pullrequest:created parser
• Create pullrequest:updated parser
• Create repo:commit_status_created parser
• Create repo:commit_status_updated parser