Add support for the new AlwaysCache attribute in the compiler and linker.
Add it to the BootstrapperApplicationData.xml along with InstallCondition.
Add them to the Burn structs and load them from XML.
Implement AlwaysCache in the engine.
Add a compiler warning if AlwaysCache is set to yes and Cache is specified.
Update History.md.
Merge branch 'develop' of https://github.com/wixbuild/wix3 into develop

Conflicts:
	History.md
Change the type of the Cache attribute to the new YesNoAlwaysType, and remove the AlwaysCache attribute.
Merge branch 'develop' of https://github.com/wixtoolset/wix3 into develop
Merge branch 'feat4329' of https://github.com/rseanhall/wix3 into develop

Conflicts:
	History.md
Merge branch 'develop' of https://github.com/wixtoolset/wix3 into feat4329

Conflicts:
	History.md
Free the right string in GetProviderInformation.
Fix History.md.
Merge branch 'feat4329' of https://github.com/rseanhall/wix3 into develop

Conflicts:
	History.md