Data Provenance: Source

[sergeiosipov]

Rationale:

Information about the Source is a part of the Data Provenance.
Source is defined by 2 entities: Source Group ("source") (specifies which source it is as a group e.g. "Bank1") & Source Version ("source_version") (specifies the exact source's versions which should be grouped e.g. "Bank1_v1.2.3").

To Do:

1. Remove already implemented text fields below from all data entities according to the section "Affected Entities" in Data Provenance #99:
   1. source_version_calendar
   2. source_version_semantic
2. Add user-defined Source Group ("source") entity, which should have at least following fields:
   1. user_code
   2. name
   3. short_name
   4. public_name
3. Add user-defined Source Version ("source_version") entity, which should have at least following fields:
   1. user_code
   2. name
   3. short_name
   4. public_name
   5. source_group
   6. version_sematic
   7. version_calendar
4. When Space is created - autocreate - (dash) instances of Source Group ("source") & Source Version ("source_version") entities.
5. Both these entities should have their own Entity Viewer Pages with CRUD operations.
6. The both entities should be a relation type of Transaction Types Input.
7. Add both these relations to the base transaction so that we can aggregate/filter by them in Transaction, Balance and PnL Reports.