Increment version to v0.7.0
Updated to Nuget 2.7 and preserved the existing logic of loading default settings
Removed callbacks from IPackageInstaller and IInstallationProvider - replaced with ILog
updated tests to reflect the removed callbacks
removed callbacks from PackageAssemblyResolver and replace with ILog. Also updated tests.
upgraded tests projects to use Nuget 2.7 too. scriptcs build version should be alpha
Merge branch 'dev' of https://github.com/scriptcs/scriptcs into stuff

Conflicts:
	src/ScriptCs.Hosting/Package/NugetInstallationProvider.cs
	src/ScriptCs.Hosting/Package/PackageInstaller.cs
	test/ScriptCs.Core.Tests/PackageAssemblyResolverTests.cs
Merge pull request #451 from filipw/nuget-upgrade

Nuget.Core upgrade to 2.7, removed old callbacks
updated to NuGet 2.7
added missing guard clauses
Merge pull request #454 from adamralph/guard-clauses

Updated to NuGet 2.7 and added missing guard clauses
Fixing small bug in ShouldNotReturnNonManagedAssemblies Test
See here: https://github.com/scriptcs/scriptcs/commit/a07ea4d2006be5338d51add0fdc83caa56d3a193#L5R67
Merge pull request #457 from johnduhart/testfix

Fixing small bug in ShouldNotReturnNonManagedAssemblies Test