Removes obsolete projects

This commit removes obsolete projects. The projects removed:

- AudioBrowser was a GUI developed for viewing LDFC spectrograms but is now unmaintained
- Dong.Felt is code that belonged to Xueyan Dong. Relvant code, mainly calculation of ridges, has been previously ported.
- QutBioacosutics.Xie is code that belonged to Jie Xie. It is not clear whether this code has been reused, but it is unmaintained.
- FELT/* projects were code created by Anthony Truskinger. The code is no longer functional and since being written has been superseeded by better techniques

All the code deleted here has been backed up in the archive copy of audio-analysis.

This is work done for #140 - open sourcing our code. This commit is non-buildable.