Thumbnails cache and size

[rpeyron]

Hi,

Thanks for Comics++

Here are two feature requests in the File browser :
- add a cache for thumbnails : I use folders with 100+ pdf files, and Comics++ is very slow to display thumbnails and restart from scratch every time i use the file browser
- change thumbnails size : allow the user to change thumbnails size as in windows explorer would be very nice

I can provide some help if you want (never done specifically C++/CX but experienced in C++)

Best regards
Rémi