Fix build warnings. Also, removed doc.xml files for debug.
Merge pull request #43 from onovotny/master

Code cleanup
Add PCL project for interfaces
Split IFilesystemProvider into separate file
Remove support for .NET 4, SL and WP7.x as Rx doesn't support them for PCLs
Move IBlobCache to Interfaces
Move extension methods to pcl
Move HttpMixin to PCL
Update NuSpecs for PCL & bumped package ver to 2.6.5
Update NuSpecs for PCL & bumped package ver to 2.6.5
Moved akavache nuspec to workaround nuget pack's relative path issues
Version bump to 2.6.5
I'm feeling brave
Fix serializing simple types

BSON doesn't like serializing just a boolean / string, we have to wrap
it in a container type.
Someday I will know how to computer.
Version bump to 2.6.6
Fix Net45 lib folder for Sqlite3
Fix two tests so they run for SQLite3 too
Add a test that supposedly works for GetAllKeys
Fix a race condition where disposing a SQLite IBlobCache could tank a different one