Link particle emitter in scripting API docs
Improve ParticleEmitter documentation. Closes #5.

Issue #5 actually wasn’t an issue, the particle emitter can be
created as expected and it works. However, missing documentation
may have been the cause, so this commit should fix the problem,
especially as it adds an example to the particle emitter documentation.
Merge branch 'release-2.0.0' of git://github.com/xet7/TSC into release-2.0.0
Catch exceptions on save loading. Fixes #160.
Update POT file /cc @xet7
Some new translatable strings. Fixes #217. /cc @xet7
Add modified hill and hedge graphics by @DarkAceZ. Closes #236.
Remove reminiscences of background preview left by commit df54a35623469a0a7672df905cb4f114d8d78e54.

It’s confusing if there’s a label “Preview” that simply doesn’t mean
anything.

Cf. ticket #156.
Add new jewel collection sounds. Closes #209.