LibreSignage v1.0.0-beta-1 release

This is the first beta release in the LibreSignage v1.x.x series.
This beta includes major changes in the web interface as well as
lots of bug fixes and other changes. The full, though not exhaustive,
changelog is included below.

v1.0.0
  - [internal] Modularize and improve the build system.
  - [feature]  Implement an improved configuration file loader that
               supports loading configuration from multiple files.
  - [feature]  Implement functionality for building LibreSignage
               Docker images.
  - [bugfix]   Fix a bug that prevented removing slide assets that didn't
               have a thumbnail.
  - [internal] Improve display animation performance by optimizing
               CSS and JavaScript. Browsers are now also hinted to use
               GPU acceleration for rendering the display.
  - [bugfix]   Fix dialogs not appearing correctly on the documentation
               pages.
  - [bugfix]   Fix a bug where adding media to user-created slides didn't
               work. (#27)
  - [feature]  Implement a new tag [font] in the markup transpiler for
               changing fonts in slides. (#28)
  - [bugfix]   Fix a missing class definition that caused problems when
               uploading files.
  - [bugfix]   Fix a bug where the editor media uploader popup didn't
               close when the (X) button was clicked if an uploade had
               previously failed.
  - [feature]  Allow space characters in upload filenames.
  - [bugfix]   Implement automatic slide lock cleanup on logout.
  - [feature]  Rewrite the web interface to use a Model, View, Controller
               architecture. Various JavaScript components used in the
               interface were also rewritten in the process.
  - [feature]  Create a LibreSignage logo and use it throughout the
               web interface.
This tag has no release notes.