Seperate RPC commands for DEx actions

[dexX7]

As discussed in #47 (comment).

Instead of:

sendtrade_OMNI "fromaddress" propertyidforsale "amountforsale" propertiddesired "amountdesired" action

There should be seperate commands for each action, for example:

sendtrade_OMNI "fromaddress" propertyidforsale "amountforsale" propertiddesired "amountdesired"
sendcanceltradebyprice_OMNI "fromaddress" propertyidforsale "amountforsale" propertiddesired "amountdesired"
sendcanceltradebypair_OMNI "fromaddress" propertyidforsale propertiddesired
sendcancelalltrades_OMNI ecosystem

The traditional DEx commands could be seperated in a similar fashion, too.

Edit: bonus points for finding an alternative to the _OMNI suffix. ;)

[zathras-crypto]

Supported.

Though commands should be eg sendtrade_OMNI rather than sendtrade to match existing naming convention (which I know there is a lack of consensus on _OMNI suffix, but that's probably a different discussion)