A few changes to Team City helper & documentation

• Parse all the properties files exposed by TeamCity to allow querying every property available. (This include a java properties file parse that isn't exposed)
• Fixes getTeamCityRecentlyFailedTests() that wasn't working anymore& change it's signature
• Replace getChangedFilesInCurrentBuild() (same reason) with TeamCityChangedFiles.get() that return a typed list of changes
• Add a few helpers for common TeamCity properties (getTeamCityBranch, getTeamCityBranchName && getTeamCityBranchIsDefault)
• Add a teamCityBlock helper to define block with the use syntax
• Fixes getBuildConfig & getProject in TC REST helpers, some properties don't exists anymore in recent versions and it was crashing the parsing
• Add a page to the website about advanced TeamCity usages with some examples

Note: The 2 changed functions are potentially a breaking change but I didn't manage to make the previous ones work and didn't find anything related to .Net app settings that it was using in TeamCity documentation.