Release Squeekboard 1.38.0

Changes:

• 25 wide shapes have been added, so that every available layout now has a wide shape
• "PgUp" and "PgDn" on the terminal-layouts have been relabeled to "Page ↑" and "Page ↓"
• The Spanish and French terminal-layouts now have translated key-names
• The Spanish terminal-layout has been updated with the additional keys that are already available on the US-terminal-layout.
• The wide and base shapes of the German layout had a different key-arrangement and the wide shape did not have a button to access additional characters; this has been fixed.

Development:

• Squeekboard's versioning now follows Phosh's versioning (for example: Squeekboard 1.38 was released in time for Phosh 0.38)
• The build-system has been simplified
  • A single Cargo.toml file is used, instead of assembling it from multiple parts
  • Newer dependencies are now used for building Squeekboard by default
• Squeekboard's main development-platform is now Debian Testing
• The layout-files have been cleaned up, so that those are easier to understand and edit