mode specific information for instruments

[djeanner]

concerning
src/general/Instrument.d.ts
Could we have additional fields for instrument specific information.
For example, in NMR, the probe head type (BBI, etc.)

[kjappelbaum]

we decided that we'll have a settings type "custom" for every technique that stores the relevant parameter and will move the other parameters in parsed, but not standardized, form to some meta field similar to how it is done at the moment.