Reorganize project files

- Move Jabber- and XMPP-specific classes into a "core" project
- Separate "bedrock" into its own project
- Change namespace to use the "kixeye" prefix
- Change namespaces to use camel-case capitalization, per .NET standards
Remove installer; we want to offer a library and not an executable
Remove docs folder from repo; build your own docs

- Update .gitignore to reflect recent changes