ERC20-connector: check the proof acceptance by tx height

[sept-en]

• Check the proof's acceptance by checking its tx height in block_header_lite
• The proof should be coming not from the ancient block
• Ancient block is defined as any block which has tx height less than minBlockAcceptanceHeight

The follow-up PR for #82. The previous PR was already reviewed and approved and this one is needed in order to merge the master branch.