Hxl-proxy

- require libhxl==4.8.3 for critical features and fixes

- hotfix for installation problem with 1.8 (in a clean install)
- require libhxl==4.8.2
- DOCKERFILE updates

- add __version__ attribute to module
- add /about.html
- change format of HTML validation error report
- when the validation error format is JSON, report other errors in
JSON as well
- add new POST endpoint /actions/validate (allows either
uploading or providing a URL for both the schema and the
content). Details: https://github.com/HXLStandard/hxl-proxy/wiki/Validation-service
- fixed bug preventing changing custom validation schema in
/data/validate
- added PyCharm project file

- require libhxl==4.7.1 for date-parsing hotfix

- add a /pcodes endpoint to download lists of P-codes
- update to support new libhxl-python hxl.datatypes module (remove
references to hxl.common)
- add JSON output option for data validation (/data/validate.json)
- show expected value in a validation error if available
- fix bug with logging into saved recipes from some pages
- allow sending an inline schema with the schema_content param
(GET or POST)

- add lat/lon to clean-data filter
- add purge option to clean-data filter
- support using MySQL as an alternative to SQLite3 for saved recipes
- default to an in-memory database for unit testing
- fix form for advanced JSON recipes
- fix template error for updating tagger in a saved recipe