ReaLearn: A couple of little QOL improvement requests :-)

[HeikoBloemers]

hello!

I have a couple of little QOL improvement requests for ReaLearn.
I know that this might not be a priority (I remember @helgoboss saying somewhere that a complete ReaLearn UI overhaul would be nice but is out of scope at the moment) but working a lot with ReaLearn currently made me want these little things so here goes:

• support background color for mappings
• support ability to select multiple mappings at the same time in order to reorder, delete, etc.
• support drag and drop to reorder mappings (either instead of or in addition to the up/down arrows?)
• support open “Edit” mapping dialog via double clicking the mapping area
• add a preference checkbox (disabled by default) “only allow one Edit dialog to be open at a time”
• upon moving a mapping into another group stop scrolling the mapping list back to the top

if any of these not very detailed requests require further elaboration please let me know and I'm happy to elaborate :-)

let me know what you think and thanks for your consideration!