Add support for submethod handling fees

[teemukontio]

Added support for defining handling fees for each submethod under each payment method including Collated.

For example, with "10;FI01=5;FI06=7.5" the fee in quote gets resolved based on selected method in a following way:

• FI01 gets a fee of 5
• FI06 gets a fee of 7.5
• Other methods in that group get a fee of 10

[Svea-Maintainer]

Tested without issues. Thanks Teemu.