BE: improve matchmaking

[malfple]

• avoid same words
• avoid 2 similar layouts so that the above can be fulfilled more easily
• match layouts that are closer in rating

[malfple]

implement avoid same words (not 100% chance) and avoid 2 similar layout.

Found out that just the key difference is not enough to determine layout similarity. Each key must be weighted (TODO)

[malfple]

also

• avoid layouts that are similar to the base layout