* add null checks before resuming a download
* (MissionAdapter.java) reset percent after resuming a download. prevents the "Error" string get stuck, until the download start
* fast download pausing
* fix UI thread blocking when calling pause()
* check running threads before start the download
* fix null pointer exception in onDestroy in the download service, without calling onCreate method (android 8)
* misc code clean-up
* fix weird download speed, before switching the list view
* fix CircularFile.java getting stuck on post-processing huge files >2GiB
* keep crashed post-processing downloads visible to the user
* fix content length reading
* use float overflow. Expensive, double is used instead
* fix invalid cast after click the mission body
* use a list for maximum attemps (downloads)
* minor clean up (DownloadManager.java)
* dont pass SharedPreferences instace to DownloadManager
* use a switch instead of checkbox for cross_network_downloads
* notify media scanner after deleting a finished download
* use bold style in status (mission_item_linear.xml)
* fix download attemps not begin updated
* dont stop the queue if a download fails
* implement partial wake-lock & wifi-lock
* show notifications for failed downloads
* ¿proper bitmap dispose? (DownloadManagerService.java)
* improve buffer filling (CircularFile.java)
* [Mp4Dash] increment reserved space from 2MiB to 15MiB. This is expensive but useful for devices with low ram
* [WebM] use 2MiB of reserved space
* fix debug warning if one thread is used
* fix wrong download speed when the activity is suspended
* Fix "Queue" menu item that appears in post-processing errors
* fix mission length dont being updated (missing commit)
