Final Code changes for R5 release
## Validator Changes
* Fix NPE validating maps
## Other code changes
* Refactor Loader for easier loading of earlier versions
* Fix various NPEs from version conversion testing
* First draft of Code generation for Extensions
* Improve summary message for map conversion outcome
* Move web path out of userData into resource field
* Fix FTP problem on windows (remote seperator)
* Update tests to use R5 package from test case repo everywhere
* Finish removing population type
* Rebuild .index.json if it's empty when installing a package
***NO_CI***
## Validator Changes
* Fix up stated path in CodeSystemValidator
* Validate example URLs in value sets correctly
* Fix problem with composition library reference in R4
## Other code changes
* More work to sort out mappings
* Fix broken links in FMM & standards status levels
* Fix type of IG-parameter extension
* FTP: Stop re-initializing file type and mode with each upload (#1178) …
* Fix snaphot generation warning when when profile-element is used
* fix path failure in tests
* Inline help16.png when generating narrative
* Suppress img.src=data content when rendering narrative
* Suppress value set expansion for core value sets that tx.fhir.org is getting wrong
* Fix NPE in profile comparison
***NO_CI***
## Validator Changes
* Fix problems validating variables
* No longer ignore hl7.org/fhir/tools when validating
## Other code changes
* Fixed bug with incorrect parameter type when POSTing a $validate-code request to a remote terminology server
* Fix OS issue with zipslip protection
* Fix for where profile_element extension was being ignored when checking types after snapshot generation
* Fix generated name for FML rules to be a valid name
* Allow loaders to decide which resources to load into the context
***NO_CI***
## Validator Changes
* Don't validate codes in value sets if terminology vlidation is turned… …
* Fix nPE validating bundles
## Other code changes
* Add file: to URL scheme list when checking for absolute URLs
* Adjust mappings handling code generating snapshots
* More improvements to r4/r5 transform testing
* Better error messages setting properties when transforming
* Better error messages converting types
* FHIRPath tests on element model
* Refactor FTPClient to perform fewer directory creates (#1159) …
* Document how to build validator_cli locally (#1171)
***NO_CI***
Grahame Grieve
markiantorno
Grahame Grieve
Michael Lawley