Added support for EntLib 6.0

Addresses issue #31.
Required addition of a .NET 4.5 target in nant build file and therefor a
tweak to nant config file.
Added Common.Logging.EntLib60.xml to gitignore
Merge branch 'master' of github.com:adrianhopebailie/common-logging into adrianhopebailie-master
 adjust references from Common.Logging.Core back to Common.Logging
substitute Common.Logging.Portable for Common.Logging.Core in sln references
remove call for specific .NET runtime in NCOVER Console params to avoid issues propertly differentiating between .NET 4.5 vs 4.51 vs. 4.5.2
silly tooling tweak to make VS 2013 happy w the project reference
commit overlooked namespace decriptor doc for entlib 6.0 support
Merge branch 'adrianhopebailie-master'
Merge branch 'master' of https://github.com/net-commons/common-logging