add memory buttons to search & query

[westram]

Add memory function (similar to calculators) to search&query window(s):

Button	Action
M+	add queried species to memorized
M-	remove queried species from memorized
MC	forget memorized species
MR (or an arrow <-)	restore memorized species as queried

Add a display field showing number of memorized species (like display of hits).

Implementation:

Use one of the database entry flag-bits.