#53 Split participant identification method

[Lukasz Salwinski]

Following the discussion in Lyon the field is actually used to convey two different pieces of information:

a) a method used to identify a given participant
b) a method used to detect a given participant is
present in a given identification

Sometimes a) is identical with b) but it is not always
the case (most common case here is a - predet, b - something like anti-tag western, coomassie, etc)

Depending on experiment setup a), b) or both are needed to describe it. This creates serious problems when
a and be are different.