Move source code src/EventStore -> src/ and reorg

This has been needed for a while, as the paths are stupidly long in some
cases:

- Change solution files to point to build location one level less deep
  than previously
- Move UpgradeProjections into etc rather than src
- Modify build scripts to point to the new src directory
- Modify packaging scripts to point to the correct location
- Remove some unused scripts and mono patches which are no longer required
- Move solutions other than EventStore.sln into src/other-solutions (this
  makes it significantly less annoying to use OmniSharp since it searches
  the directory tree for the nearest solution file prompts if it finds
  more than one at the same level).
Credit other OSS in the license