various small imrpovements by WabinabUknown

[lennczar]

This issue summarized the feeback by WabinabUknown (#98)

• Default gas unit should be TGas everywhere
• Increase visibility of "+" add column icon (might go with Improve accessibility #76)
• Explain 1 NEAR multicall creation fee (might go with add some Tooltips and helpful placeholders #73)