Borb

This is a bugfix release.

This is a bugfix release.

With this release, `borb` is one step closer to being able to write a PDF/A-1b document.
We still need to create an `\OutputIntents` Dictionary in the document to be fully compliant.
This is planned for the next release.

This release features:

- Minor bugfix to estimating width of a space character
- Useful in text extraction
- Bugfix in `TrueTypeFont` to build a proper `\Widths` array and `cmap`
- Fixes in `XMPDocumentInfo` class
- Title
- Author
- Creator
- CreatorTool
- Separate logic that writes `\Info` `Dictionary`
- This class now also writes the `XMP` `\Metadata` when needed
- Enables PDF/A-1b
- Added tests for PDF/A-1b (preservation of metadata)

This release features:

- Minor bugfix to `LayoutElement` to ensure `\Resources` dictionary gets initialized.
- Added asserts to ensure password-protected documents are handled properly.

This release features:

- minor bugfix to previous `add_event_listener` - refactor
- First effort to implement PDF encryption
- Currently support for `StandardSecurityHandler`
- RC4
- MD5

This release features:

- Changes to layout of text LayoutElement(s)
- Support for `multiplied_leading`
- Support for `fixed_leading`
- Small fix to text justification algorithm

- Updated the test to comply with the new behaviour

- Added legal stuff to the library
- BORB_CONTRIBUTOR_LICENSE_AGREEMENT.md
- CONTRIBUTING.md

- Added an extra test/showcase
- Creating a flyer using PDF graphics

- Removed EventListener options on PDF objects
- EventListeners are now part of the parsing process, rather than the object
- EventListeners are passed around during parsing
- Objects are more lightweight