Squashed 'Telerik.Sitefinity.Samples.Common/' changes from a17eb52..2eb2bb8

2eb2bb8 Updated references
c1961d3 Fixed blog posts duplicate creation on system restart
74d36c5 Upgraded to Beta HF 1 (7.1.5141.0)
bcb289e Changed the check for existing thread
6d0290e Updated hintpaths
f049418 Updated import directive condition
52b0011 Merge branch 'review' of https://github.com/Sitefinity-SDK/Telerik.Sitefinity.Samples.Common.git
fc3bd09 Updated versions when SitefinityWebApp condition
91cbdc9 Updated .csproj improt StyleCop condition
05b3b74 Upgrade to Sitefinity 7.1 Beta

git-subtree-dir: Telerik.Sitefinity.Samples.Common
git-subtree-split: 2eb2bb8fbfce025cd1d85da8da867a55a893966e
Merge commit '382cab70abf232c9a4d547b5001a1da5c8385ab4' into review
Upgraded to SF 7.1.5141.0-beta
Added official NuGet package source in NuGet.targets