persistent property library

[vstadnytskyi]

The original icarus NMR control software library relied on persistent property library, a home-developed library by Friedrich Schotte. The dependency need to be resolved. There are two solutons

1. embed the library into icarus library
2. create a separate repository for the library and add it to PyPi. This will require Friedrich to maintain GitHub library.

[vstadnytskyi]

I decided to strip it off and just have default values saved in the classes. The idea behind persistent property library is to have some values from different processes to be saved to a hard drive and retrieve them later