WIXFEAT: 4190 - Self updating bundles.

- core cleanup after code review
- added history entry
Add ApprovedExeForElevation element, IBootstrapperEngine::LaunchApprovedExe, IBootstrapperApplication::OnLaunchApprovedExeBegin, IBootstrapperApplication::OnLaunchApprovedExeCompleted, and enable WixStdBA to use them.
Format the arguments sent to LaunchApprovedExe, and address feedback.
Merge branch 'NetFxExtension-4.5.2-support' of git://github.com/gordonmcshane/wix3 into develop
Merge branch 'develop' of https://github.com/wixtoolset/wix3 into develop
Merge branch 'testfixes' of git://github.com/heaths/wix3 into develop
WIXFEAT: 4190 - Self updating bundles.

- core cleanup after code review
- added history entry

Conflicts:
	History.md
Fix formatting bug with long strings

There was an issue where long strings could not be formatted back into themselves when calling the secure functions to zero memory. This will still zero the original memory block of the reallocated block is at a new address.
Merge branch 'develop' of https://github.com/wixtoolset/wix3 into develop
Merge branch 'relbundles' of git://github.com/heaths/wix3 into develop
Merge pull request #86 from heaths/relbundles

Fix formatting bug with long strings
Merge branch 'develop' of https://github.com/wixtoolset/wix3 into develop
Merge branch 'feat3249rebased' of git://github.com/rseanhall/wix3 into develop

Conflicts:
	History.md
Securely free the strings when launching an approved exe, and address feedback from 3249.
Merge pull request #88 from rseanhall/feat3249cleanup

Cleanup from 3249
Add CONTRIBUTING.md

Per https://github.com/blog/1184-contributing-guidelines
Merge pull request #90 from barnson/AddContributing

Add CONTRIBUTING.md
Merge branch 'develop' into Wixfeat4190.2

Conflicts:
	History.md
Removed commented out error type constant.
Merge branch 'Wixfeat4190.2' of github.com:jchoover/wix3 into Wixfeat4190.2

Conflicts:
	History.md
	src/burn/inc/IBootstrapperApplication.h