Evaluate user needs for presence of storage fields

[thpani]

The presence of storage fields is different between instance and persistent/temporary storage:
All instance data is stored in a single LedgerEntry, thus all instance fields are present if a single instance field changes.
persistent/temporary have one LedgerEntry per field, thus they are only present in the transaction meta if that field changes.

Currently (#123), this behavior is mirrored by Solarkraft, i.e., persistent/temporary are only present as storage fields if they are modified by the transaction.

We'll need one (or a few) case studies to determine if the current behavior is enough, or if we indeed need access to fields untouched by the transaction. If the latter is the case, we'll need to

1. make the monitors stateful (accumulating historical transactions), or
2. proactively fetch all persistent/temporary fields (an open question is how we'd know which fields exist)