Mirador 2.3.0 - New Annotation Features, Toolchain Improvements, and Bug Fixes

• Fix multi-window annotation behaviour so that windows no longer conflict with one another, resolving a number of related bugs.
• Added the option to specify line thickness on annotation regions
• Fully namespace CSS by abstracting the styles into LESS, improving developer experience and preventing host-page styling conflicts.
• Add options to handlebars to prevent conflicts with a containing page's use of handlebars.
• Updates develop mode of build system to watch style changes correctly.
• Testing improvements to cover more modern node versions and to more fully test the behaviour of multi-windowed annotation.
• Fix a problem with annotation deletion in which a popup appeared underneath its black background, preventing user interaction.
• Improve error handling in annotation code by allowing annotation to continue after an attempt to load an annotation fails.
• Improve embedding behaviour by dismissing annotation regions and pop-ups when the mouse leaves the Mirador container element.
• Repair a bug in the annotation rendering that caused boxes to appears larger than their coordinates described, making them overlap.
• Add missing locales and translation tokens.