…aces and to simplify and align implementations.

* Completed code to support Metapath array construction.
* Implemented array postfix and unary lookups.
* Cleaned up ISequence implementations, moving getFirstItem to be a method member. Added a utility function to convert a sequence into an array member.
* Added support for the following Metapath functions:
  - array:get
  - array:put
  - array:append
  - array:subarray
  - array:remove
  - array:insert-before
  - array:join
  - array:head
  - array:tail
  - array:reverse
  - array:flatten
* Fixed spotbugs null check warnings
* Cleaned up some Javadocs.
* Incorporated changes based on CodeRabbit review.
* normalized line endings

* Added initial implementation of the 'metaschema-cli metapath list-functions' command.
* Added a better means to collect the metaschema-related CLI commands for reuse.

… returns the root node when getValue is called.

- Support for map construction.
- Added support for maps in function call, postfix and unary lookups.
- Added support and unit tests for the following Metapath functions:
  - map:get
  - map:merge
  - map:entry
  - map:size
  - map:keys
  - map:contains
  - map:find
  - map:put
  - map:remove
- Added missing characteristics on a number of existing Metapath functions.
- Cleaned up a bunch of PMD warnings.

…function signatures now instead of the Java class name.

… use. Improved abstract CLI validation commands to provide more options for model detection.