Database Docs Update (database.rst)

Modified the doc entry for "Connecting and initializing the database"
Database Docs Update (database.rst)

Edited "Adding new Entries" main article
Database Docs Update (database.rst)

Modified "Removing Entries"
Database Docs Update (database.rst)

Broke down the Markdown Bullet list lines into multiple lines
Merge pull request #991 from rajul-iitkgp/database_docs

[DocFix]: Edited SunPy Database module docs