Add security to Hidden Burn Variables by calling SecureZeroMemory on the value, encrypting the value, and adding SecureStringVariables to the managed Engine.
Make StringVariables use pointers so that the IBootstrapperEngineSecure interface can be deleted.
Consolidate the StrUtil Secure methods so the code isn't duplicated.
Formatting.
Merge branch 'develop' of https://github.com/wixtoolset/wix3 into wixfeat4299
Fix bugs.
Add the WixBundleNumberOfApplyPhases built-in variable.
Convert WixBundleNumberOfApplyPhases variable to IBootstrapperApplication::OnApplyNumberOfPhases.
Merge pull request #6 from rseanhall/wixfeat4299

Conflicts:
	src/burn/engine/exeengine.cpp
Merge pull request #28 from rseanhall/feat4413

Conflicts:
	History.md