#19 Release notes updates for v0.1 + documentation improvements.

#19 (closed) Release notes updates for v0.1 + documentation improvements.

• Updated/extended released notes for v0.1.
• Removed '(unreleased)' annotations in release notes.
  • Difficult to keep up-to-date.
• Added more documentation cross-linking (ESCET to/from languages).
  • Using actual online URLs, which are now known.
• Cross-linking information extended with what you'll find there.
• Refer to website for development information.
• Our tools are also available as plug-ins from an update site.
• Some other small textual changes in documentation.

Closes #19 (closed)