capnp schema needs version control coupled with tags on this repo

[ktugan]

It is currently impossible to determine the capnp schema version and needed code-version.

Add a new field to FrameContainer which allows to see what version the schema is on:

struct FrameContainer {
  id @0 :UInt64;                    # global unique id of the frame container
  dataSources @1:List(DataSource);  # list of data sources (videos / images)
  fromTimestamp @2 :Float64;        # unix timestamp of the first frame
  toTimestamp @3 :Float64;          # unix timestamp of the last frame
  frames @4 :List(Frame);           # frames must be sorted by in the order they where recorded.
  camId @5 :UInt16;                 # the cam number
  hiveId @6 :UInt16;                # the id of the hive
  transformationMatrix @7 :List(Float32);
                                    # the transformation matrix from image coordinates to hive coordinates.
                                    # The matrix is of dimension 4x4 and stored this way
                                    #     1 | 2 | 3 | 4
                                    #     5 | 6
                                    #          ...
                                    #             15| 16
schema_version: @8 :UInt16; # the version of the schema
}

I also propose to tag each version the code (this repo) with following schema:
v[schema_version].[minor_version]
schema_version is the capnp-version the code is supporting
minor_version is incremented when code changes are happening which do not break the schema

This allows our legacy projects to be still supported and even get some necessary updates. Old projects will otherwise break on every change.