Feature/#187 udpdate to exist 5 3 0

Feature

Summary

This MR provides an update to eXist-db 5.3.0 with the necessary changes. According to the release notes the most important changes we have to consider are:

• Duplicate functions will reliably throw a useful error
• Made fn:collection spec compliant

Compliance to “Definition of Done”

• Unit tests passed
• Code reviewed
• Product Owner accepts the User Story

Documentation

• I updated the README (if applicable)
• I provided my functions with appropriate documentation
• I updated existing documentation

Tests

Are we able to test this new feature?

• Yes, everything can be done via unit tests.

Changelog

• I added a statement to the CHANGELOG.

Version number

• I bumped the version number in build.properties.

Closes

Closes #187 (closed)

/cc Mathias Göbel, Frank Schneider, Michelle Weidling