cache - allow access to old (outdated) entry when creating cache entry

this allows to reuse the SourceText object which will enable incremental
parsing/updating of syntax trees
buffersync - introduce a SourceTextService to allow buffer updates

Makes the Rolsyn compiler ask for source text from a service when building
syntax trees. Allows to record source text changes when a corresponding
messages is being received
buffersync - incorporate feedback
buffersync - incorporate feedback
buffersync - incorporate feedback
buffersync - sorted usings
Merge pull request #767 from jrieken/buffersync

dth - enable buffer updates outside the file save cycle
Fixed tests and updated project references.
Add all folders to the cache dependency (prelim until file watcher work is in)
Updating to release NuGet.config
Merge branch 'release' into dev
Updating to release NuGet.config
Merge branch 'release' into dev
Switching to dev NuGet.config
Use synchronous operations on ZipArchive in CoreCLR
Add "kpm wrap" command

- Add CsprojDumper, a tool used to dump csproj references
- "kpm wrap" creates project.json wrappers for csprojs in 'wrap' folder
- "kpm wrap" updates global.json to include 'wrap' folder as sources