Update labels in Asset/Atomic Swaps to avoid confusions

[dbadol]

Current situation
In current wallet (v7.5) the asset swap and atomic swap offers say "SEND" on one side and "RECEIVE" on the other. It is not always completely clear who is sending and who is receiving, in particular when mixing our own offers to existing offers.

Solution we propose
Replace "SEND" by "I SEND" and "RECEIVE" by "I RECEIVE", to be very clear on what side of the swap the user would be.

Remarks

• We need to verify that the current display order of the offers in the list indeed matches this logic.
• The use of "I" (instead of "You") is consistent with the label used in tab "MY OFFERS".

Mockups
Screenshots with the proposed text.