Support reagents and conditions in CML

_Business need_:

Reagent - substance that can be added to mixture of reactants to trigger a chain of chemical reactions. Reagent is not consumed during chemical reaction.
Chemical condition specifies the condition under which the reaction shall go (temperature, UV etc.).

1. System shall detect reagent(s) and conditions from ket as molecule/text that is located above or below an arrow (in the area bounded by perpendiculars passing through the end of the arrow).

2. System shall write reagents and conditions information in cml format according to format specification.

3. System shall communicate reagents and conditions information in cml format to Ketcher.

4. Indigo shall be able to retrieve reagents and conditions from cml and write them into ket format.