Update lang/pl_PL.lang

Fixed some typos and forms, updated missing strings. Checked for grammar and style mistakes.
Rework libspotify downloader and att support for libspotify on rpi
Add a concept of "built-in" plugins and let Spotify be such a thing
Rename Plugins -> Apps
Add static_assert()
buf: Add buf_retain()
Improve blobcache

Write to disk in a separate thread to avoid blocking callers if flashs are slow
Make index storing much more robust
osx: Fix libspotify build
Fix incoorect type
blobcache: Fix uninitialized var
Add a websocket server

Also we have a websocket echo service right now at :42000/showtime/ws/echo
No longer include htsmsg/htsmsg_store.h from showtime.h
prop: Add support for PROP_SET_FLOAT to prop_set() and friends
prop: Add prop_setdn()
httpserver: NUL terminate websocket packets
httpserver: If websocket init code returns error, send it in HTTP response
htsmsg: HTSMSG_INDEX() instead of name returns indexed field for htsmsg_get_...() functions
gvl: Handle integer types in changed()
Initial stab of STPP over websocket

STPP is Showtime Property Protocol that allows remote access to
all of Showtime's internals and in should in the end be capable
of supporting fully featured remote control apps
prop: Add alternative path resolution when subscribing