Reorganize packages, closes #79

- All packages go into either cmd or pkg directories
- Most packages renamed
- Server packages moved into pkg/server
- sanitize moved into webui, as that's the only place it's used
- filestore moved into pkg/storage/file
- Makefile updated, and PKG variable use fixed

.gitignore

@@ -26,8 +26,12 @@ _testmain.go
 *.swo
 
 # our binaries
+/client
+/client.exe
 /inbucket
 /inbucket.exe
 /dist/**
 /cmd/client/client
 /cmd/client/client.exe
+/cmd/inbucket/inbucket
+/cmd/inbucket/inbucket.exe