Added update of nuspec files

- Sets the version of nuspec files in a project directory to correct version, excluding build data
- Added ToString method to Semver class that takes a format specifier
Refactored scanning

- Changed -scan switch to be false by default
- -version flag overrides any version.txt
- Writing full semantic version to AsseblyInformationalVersion
Added listing of resolved versions in project structure

- Uses project scanner to resolve versions of projects
- Displays project path and version per project