0.23.0

Add a new colorizations <true|false> command to enable/disable asynchronous
provision of colorization information following a parse: #60 (Fixes #44).
Newest FSharp.Core is used for type-checking scripts and for projects that
do not reference FSharp.Core. Supports F# 3.0, 3.1 and 4.0: #59.
If MSBuild v12 is not available, instead try load MSBuild v14. This, together
with the previous point, adds support for VS2015-only Windows installs: #57.
Fixes: #12 #21 #23 #25 #54.
Backwards-incompatible: compilerlocation command has changed. Now provides
path to best version of msbuild, fsc and fsi on Windows: #23.