add fields that should be shared by all spectra

the following fields

```
{
createdBy:
date:
temperature (object):
SI (number):
unit (string):
instrument: {
model:
manufacturer
serialNumber:
software:
}
procedure (html):
report (html):
}
```
should be shared by all spectra (we can also clarify this in the `README.md`)

`description` should not be used.

@lpatiny For date, I saw both ms since unix epoch and ISO 8601 formatted date, which ones should we use?